HYMC 0001718405-22-000008 8-K as filed: Feb 22, 2022



			Technical Report Summary of Initial Assessment on the Hycroft Mine Nevada, United States of America Effective Date: February 18, 2022 Prepared for: Hycroft Mining Holding Corporation (4300 Water Canyon Road, Unit #1, Winnemucca, NV 89445 USA) Prepared by: Ausenco Engineering USA South Inc. (595 S. Meyer Ave. Tucson, AZ 85701 USA) Independent Mining Consultants, Inc. (560 E Gas Rd., Tucson, AZ 85714 USA) WestLand Engineering & Environmental Services, Inc. (4001 E. Paradise Falls Drive, Tucson, AZ 85712 USA)

Table of Contents


1 Executive Summary			1
1.1 Introduction			1
1.2 Project Setting			1
1.3 Mineral Tenure, Surface Rights, Water Rights, Royalties and Agreements			1
1.4 Geology and Mineralization			2
1.5 History			2
1.6 Exploration, Drilling and Sampling			3
1.7 Data Verification			3
1.8 Metallurgical Testwork			3
1.9 Mineral Resource Estimation			4
1.10 Conclusions			5
1.11 Recommendations			6
2 Introduction			7
2.1 Overview			7
2.2 Qualified Persons			7
2.3 Site Visits			8
2.4 Effective Dates			8
2.5 Sources of Information and References			8
2.6 Previous Technical Report Summaries			8
2.7 Units and Abbreviations			8
3 Property description and location			11
3.1 Introduction			11
3.2 Property Ownership and Title In (Jurisdiction)			13
3.3 Land Status			13
3.4 Property Agreements and Royalties			17
3.5 Water Rights			17
3.6 Liabilities & Encumbrances			17
3.6.1 Environmental Liabilities			17
3.6.2 Mine Safety Disclosures			18
3.6.3 Operating Permits			18
3.6.4 Hycroft Expansion Permitting and Timelines			20
3.6.5 Crofoot Heap Leach Facility Closure			21
3.7 Environmental Considerations			21
3.8 Social License Considerations			22
4 Accessibility, climate, local resources, infrastructure and physiography			23
4.1 Access			23


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4.2 Climate			23
4.2.1 Local Resources and Infrastructure			23
4.3 Seismicity			24
5 History			25
5.1 Property History			25
5.2 Mining History			25
5.3 Exploration History			26
5.4 Production History			28
6 Geological setting, mineralization, and deposit			30
6.1 Geological Setting			30
6.1.1 Regional Geology			30
6.1.2 Local Geology			32
6.1.2.1 Brimstone			32
6.1.2.2 Vortex			33
6.1.2.3 Bay and Boneyard			35
6.1.2.4 Central			35
6.1.2.5 Camel Hill and Cut 5 Zones			36
6.2 Alteration and Mineralization			36
6.3 Deposit Types			37
7 Exploration			38
7.1 Drilling			38
7.2 Additional Exploration			40
8 Sample preparation, analyses, and security			41
8.1 Sample Preparation			41
8.2 Assay Methods			41
8.3 Sample Security			42
8.4 Analytical Results			42
9 Data verification			43
9.1 QA/QC Post 2005			43
9.1.1 Standards			43
9.1.2 Blanks			45
9.1.3 Check Assays			46
9.1.4 Certificates			48
9.1.5 Old vs. New Drilling			49
9.1.6 DDH vs RC			49
9.1.7 Downhole Surveys			50
10 Mineral processing and metallurgical testing			51


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10.1 Mineralized Materials and Sampling			51
10.1.1 Hycroft Mineralization Domains			51
10.1.2 Samples for Metallurgical Testing			52
10.2 Comminution Tests			52
10.3 Flotation			53
10.3.1 Review of Flotation Testwork			53
10.3.1.1 SGS Minerals Services (Lakefield) – March 2009			53
10.3.1.2 SGS Minerals Services (Lakefield) – Nov 2010			53
10.3.1.3 KCA Batch Tests – Jan 2011			53
10.3.1.4 KCA Locked Cycle Tests – May 2011			54
10.3.1.5 G&T Metallurgical Services Ltd. – Feb 2011			54
10.3.1.6 Hazen Research, Inc. – August 2011			55
10.3.1.7 Fitness of Grind for Flotation Tests			55
10.3.1.8 Reagent Suite			56
10.3.2 Flotation Time			56
10.4 Direct Cyanidation			58
10.5 Concentrate Oxidation Tests			58
10.5.1 Atmospheric Oxidation – Batch Tests			58
10.5.2 Pilot Plant Oxidation Tests			59
10.5.3 Hycroft Mill Demonstration Plant			59
10.5.4 Pressure Oxidation			61
10.5.5 Roasting			63
10.6 Gold Solid-Liquid Separation Tests			63
11 Mineral resource estimates			64
11.1 Model Location			64
11.2 Database			64
11.3 Basic Statistics			65
11.3.1 Geology			66
11.3.2 Lithology			66
11.3.3 Alteration			67
11.3.4 Structure			67
11.4 Domain			70
11.5 Assay Caps			70
11.6 Bench Height Confirmation			71
11.7 Composites			72
11.8 Variography			74
11.9 Block Grade Estimation			77
11.9.1 Au and Ag			77
11.9.2 Cyanide Ratio			79


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11.9.3 Sulfide Sulfur			79
11.9.4 Density			80
11.9.5 Stockpile Grade Estimation			81
11.10 Classification			82
11.11 Model Verification			82
11.11.1 Swath Plots			83
11.11.2 Smear Check			86
11.11.3 Reconciliation			87
11.12 Mineral Resources			88
12 Mineral reserve estimates			91
13 Mining methods			92
14 Processing and Recovery methods			93
15 Infrastructure			94
16 Market studies and contracts			95
17 Environmental studies, permitting, and plans, negotiations, or agreements with local individuals or groups			96
18 Capital and operating costs			97
19 Economic analysis			98
20 Adjacent properties			99
21 Other relevant data and information			100
22 Interpretation and conclusions			101
23 Recommendations			104
23.1 Introduction			104
23.2 Proposed Exploration Program			104
23.3 Proposed Metallurgical Studies			104
24 References			106
25 Reliance on the registrant			109

List of Tables


Table 1-1: Hycroft Mineral Resources as of January 1, 2022			5
Table 2-1: Unit Abbreviations			8
Table 2-2: Name Abbreviations			9
Table 3-1: Hycroft Annual Land Holding Costs			17
Table 3-2: Hycroft Operating Permits			18


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Table 3-3: Hycroft Miscellaneous Permits			19
Table 3-4: Hycroft Permits and Annual Fees			19
Table 3-5: Right-of-Way Payment and Renewal Schedule			20
Table 4-1: Hycroft Water Wells and Permitted Yearly Consumption			24
Table 5-1: Au and Ag Sales from 2019 to 2021			28
Table 9-1: Nearest Neighbor Sample Comparison of Pre-2000 Au Composites versus Post-2000 Au Composites			49
Table 9-2: Nearest Neighbor Sample Comparison of RC Au Composites versus DDH Au Composites			50
Table 10-1: Average Sulfur Contents of Oxide, Transition and Sulfide Mineralized Materials			51
Table 10-2: Summary of Test Samples			52
Table 10-3: Grindability Test Summary			52
Table 10-4: G&T Composites 1 through 24 Flotation Test Results			54
Table 10-5: G&T Composites M-1 through M-17 Flotation Test Results			55
Table 10-6: Flotation Reagent Schemes Studied			56
Table 10-7: Estimated Metallurgical Recoveries from 2016 Feasibility Study – Au and Ag			58
Table 10-8: Hycroft Alkaline POX Testwork Summary			61
Table 10-9: Hycroft Acid POX Testwork Summary			62
Table 10-10: Settling Test Results			63
Table 11-1: Block Size and Model Size			64
Table 11-2: Data Available for the Assembly of the Resource Model for Au, and Ag			65
Table 11-3: Assay Database (No Stockpile Assays)			65
Table 11-4: Population Domains for Grade Estimation			70
Table 11-5: Assay Cap Values			71
Table 11-6: Basic Statistics of 40-ft Length Composites			73
Table 11-7: Grade Estimation Parameters for Au, Ag, and Mercury			78
Table 11-8: Estimation Parameters for Cyanide Ratio			79
Table 11-9: Sulfide Sulfur Estimation Parameters			80
Table 11-10: Sulfide Sulfur Default Values if Not Estimated			80
Table 11-11: Density Assigned to the Block Model			81
Table 11-12: Stockpile Grade Estimation of Assignments			82
Table 11-13: IMC Smear Check			86
Table 11-14: Reconciliation Summary, 19 Months of Production Versus the Block Model Reporting of the Same Volume			87
Table 11-15: Economic Parameters for Mineral Resources			89
Table 11-16: Hycroft Mineral Resources as of February 15, 2022			90
Table 25-1: Information Provided by Hycroft			109


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List of Figures


Figure 3-1: Hycroft Mine Property Location Map			13
Figure 3-2: Hycroft Mine Claims Map			15
Figure 3-3: Current Property and Facilities Layout (2021)			17
Figure 5-1: Predominant Mineralization Zones Identified for the Mine.			28
Figure 6-1: Stratigraphic Column for Hycroft Deposit Area			32
Figure 6-2: Simplified East–West Cross-Sections through the Sulphur District			33
Figure 6-3: Brimstone Generalized Geology Cross-Section			34
Figure 6-4: Vortex to Camel Hill Generalized Section			35
Figure 6-5: Bay Geologic Cross-Section			36
Figure 6-6: Generalized Hycroft Epithermal Diagram			38
Figure 7-1: Drillhole Collar Locations			40
Figure 9-1: Results of Submitted Gold Standards			45
Figure 9-2: Results of Submitted Silver Standards			46
Figure 9-3: Results of Blank Submissions			47
Figure 9-4: Check Assay Results, Fire Assay Gold 2011 - 2012			48
Figure 9-5: Check Assay Results, Fire Assay Silver 2011 – 2011			49
Figure 10-1: Recovery vs. Time Plot, G&T Kamloops Tests, M Composites			58
Figure 10-2: Au and Ag Extraction vs. Sulfide Oxidation			60
Figure 10-3: Oxidation of Central Flotation Concentrate: Sulfate Spike Test			61
Figure 10-4: Demonstration Plant Cyanide Leach Recovery of Au and Ag			61
Figure 11-1: East–West Cross-Section 43,000N Looking North, showing Hycroft Rock Types			69
Figure 11-2: East–West Cross-Section 43,000N Looking North, showing Hycroft Alterations			69
Figure 11-3: Hycroft Structure Interpretation			70
Figure 11-4: Bench Height Analysis			73
Figure 11-5: Variograms for Silicic Material Between the West Splay and Central Faults			76
Figure 11-6: Variograms in Silicic Material Between the Central Fault and the East Fault Footwall			77
Figure 11-7: Vertical Swath Plots for Gold and Silver			85
Figure 11-8: Vertical Swath Plots for Gold and Silver			86

List of Appendices


			APPENDIX 1 – Hycroft Mine Patented Claims List, 2022


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1EXECUTIVE SUMMARY

1.1Introduction

This Technical Report Summary (TRS) has been prepared by Ausenco Engineering USA South Inc. (Ausenco), Independent Mining Consultants, Inc. (IMC), and WestLand Engineering & Environmental Services, Inc. (Westland) for Hycroft Mining Holding Corporation (Hycroft), following the reporting requirements of the United States Securities and Exchange Commission’s (SEC) Modernization of Property Disclosures of Mining Registrants under subpart 1300 and item 601 (96)(B)(iii) of Regulation S-K for an Initial Assessment (IA).

This TRS provides an Initial Assessment of the mineral resource estimate utilizing a milling and pressure oxidation process for sulfide mineralization and heap leaching process for oxide and transition mineralization.

1.2Project Setting

The Hycroft property (the Mine) is situated on the western flank of the Kamma Mountains on the eastern edge of the Black Rock Desert approximately 54 miles west of Winnemucca in Humboldt and Pershing Counties, Nevada. The Mine property straddles Townships 34, 35, 35½ and 36 North and Ranges 28, 29 and 30 East (MDB&M) with an approximate latitude 40°52’ north and longitude 118°41’ west.

The Mine is accessible via Nevada State Route 49 (Jungo Road), an unpaved road maintained by Humboldt County and Pershing County and Hycroft. The Union Pacific railway, a major east–west railway, runs immediately adjacent to the property.

Existing facilities on site include two administration buildings, a mobile maintenance shop, a light vehicle maintenance shop, a warehouse, leach pads, primary, secondary and tertiary crushing systems, and two Merrill-Crowe process plants, and a refinery.

1.3Mineral Tenure, Surface Rights, Water Rights, Royalties and Agreements

The Mine property consists of 30 private parcels with patented claims that comprise approximately 1,912 acres, and 3,247 unpatented mining claims that encompass approximately 68,759 acres. The combined patented and unpatented claims comprise approximately 70,671 acres. Much of the project area is located on un-surveyed public and private land. The following is a list of land acquisitions/transactions made over the years which constitute the entire Hycroft land claim package:

•The Crofoot property and approximately 3,500 acres of claims were acquired by Vista Gold Corporation (Vista) in 1985.

•The Crofoot property, originally held under lease, is owned by Hycroft subject to a 4% Net Profits Interest (NPI) retained by the former owners.

•The Lewis property and approximately 8,700 acres of claims were acquired by Vista in early 1987.

•In 2006, approximately 13,100 acres of additional claims were staked by Vista.

These claims are contiguous or proximate to the original Crofoot and Lewis claims. In 1996, the lease/purchase agreement was amended to provide for minimum advance royalty payments of US$120,000 on January 1 of each year in which mining occurs on patented and unpatented claims. The sum of payments for the Crofoot property is capped at US$7.6 M, of which US$3.0 M has been paid through December 2021. An additional US$120,000 annually is due if mineralized material production exceeds 5 Mtons from the Crofoot property on either patented or unpatented claims in any calendar year. All advanced royalty payments are taken as a credit against the NPI.

Payment of annual claim holding fees to the Bureau of Land Management (BLM) and Humboldt and Pershing Counties are made every third quarter (Q3). Payments are current through the 2020-2021 claim years, with US$589,944 paid in Q3 2021. Payment of annual land holding fees and taxes is required to continue to hold the Hycroft property in good standing. Hycroft controls all surface and mineral rights within the Hycroft mineral resource area. No further land acquisition is required for operation of the mine and processing facilities as presently designed.

Water resources at the Mine are controlled under 11 separate water right permits administered by the Nevada Division of Water Resources (NDWR). These permits are either held in ownership by Hycroft or leased to Hycroft. Hycroft controls a total of 21,457.95-acre feet per year (6.99 billion gallons per year) in the Black Rock Desert Hydrographic Basin.


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1.4Geology and Mineralization

The Hycroft deposit is a low-sulfidation, epithermal, hot springs system that contains Au and Ag mineralization. Radiometric dates indicate that the main phase of Au and Ag mineralization formed four million years ago when hydrothermal fluids were fed upward along high angle, normal faults. Low-grade Au and Ag mineralization was co-deposited with silica and potassium feldspar throughout porous rock types.

A subsequent drop in permeability, due to sealing of the system, led to over pressuring and subsequent repeated hydrothermal brecciation. Additional precious metal mineralization was deposited during this event as breccia zones, veins, and sulfide flooding.

Au and Ag mineralization was followed 0.4 to 2 million years ago by an intense event of high sulfidation acid leaching of the mineralized volcanic rocks coincident with a regional water table drop. This allowed steam heated sulfur gases to condense into sulfuric acid and leach the upper portion of the mineralized rocks.

Oxidation of sulfide mineralization occurs to variable depths over the deposit, depending upon proximity to faults, extent of acid leaching, and depth to water table. Sulfide content through the deposit can be variable but typically averages between 1.5 and 2.0% sulfide sulfur.

The Hycroft deposit is typically broken into six major zones based on geology, mineralization, and alteration. These include Brimstone, Vortex, Central, Bay, Boneyard, and Camel Hill. The boundaries are typically the major faults, namely Break, East and Ramp.

1.5History

Mining in the Sulfur District, where the Mine is located, began in the late 1800’s for native sulfur, then in the early part of the 19th century high-grade Ag was mined as were veins of nearly pure alunite (hydroxylated aluminum potassium sulfate mineral) in the southern part of the district. From 1941 to 1943, cinnabar (a mercury sulfide mineral) was also mined. Exploration for native sulfur commenced again in 1966 with the Duval Corporation (Duval) reporting elevated Au and Ag values but finding no significant evidence of a sulfur deposit at depth (Wallace, 1980).

In 1977, the Cordex Syndicate mapped and rock chip sampled the Hycroft property, recognizing the potential for a bulk tonnage, low-grade precious metal deposit. Homestake then took interest in the property and completed surface sampling and exploration drilling during 1981-1982. Mining officially began as a small heap leach operation in 1983 at what was then known as the Lewis Mine. In 1985, Vista gained control of the original Hycroft property. They also acquired the Lewis Mine in early 1987 from F. W. Lewis, Inc. and the Crofoot Mine in April 1988. From 1985 to 1999, they had drilled 3,212 exploration holes, totaling 965,552 feet (ft) with the bulk of this drilling focused on oxide gold mineralization at Central, Bay and Brimstone.

The remaining leasehold interest in the Lewis property was purchased by Vista in December 2005. Production followed at the former Crofoot property in the Bay, South Central, Boneyard, Gap and Cut-4 pits along the Central Zone. Production from the Brimstone Pit commenced in 1985 and continued until December 1998. The Mine was placed on a care and maintenance program through 2007. During 1983 to 1998, the Mine produced approximately 1.2 Moz of Au and 2.5 Moz of Ag. An additional 58,700 oz of Au was produced from the leaching operations from 1999 through 2004. In May 2007, the Nevada-based holdings of Vista were spun out into Allied Nevada Gold Corp (Allied Nevada). The Mine was included as part of the transfer of ownership allowing Allied Nevada to explore, expand, and develop the resources. The Mine was reactivated in September 2007 and achieved planned ore production by the end of 2009. With the construction of the North leach pad in 2013, the total leach pad space was increased to more than 20 million square ft. In 2010, the Mine began an expansion program that included construction of a 21,000 gallon per minute Merrill-Crowe processing plant and a three-stage crushing facility as well as solution pumping capacity upgrades. Active mining was stopped again at the Mine in June 2015 due to low metal prices, but active leaching of previously mined ore continued through 2018. During this time, Allied Nevada emerged from its financial restructuring to become Hycroft Mining Corporation. In late 2018, Hycroft began construction of new leach pads. In April 2019, active mining began with a focus on transition and sulfide minerals but were set aside for future processing. Only oxide ore was placed on the new leach pads during this time with production of Au and Ag continuing through until 2021. From September 2007 through July 2019 metal sales have totaled approximately 900,000 oz of Au and 5.0M oz of Ag. Active mining ceased in 2015 and production at the Mine was terminated on November 11, 2021. Annual sales in ounces of Au and Ag produced from the Mine’s heap leach operations over years 2019 through 2021 total approximately 90,000 ounces of Au and 570,000 ounces of Ag.


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1.6Exploration, Drilling and Sampling

The Hycroft district includes data from 1981 to 2018 and includes 5,501 holes, representing 2,482,722 ft of drilling. At this time, there are 5,323 drillholes in the resource model area of which 134 have been drilled to define stockpiles or the Crofoot leach pad.

In addition to drilling activity, Hycroft has also conducted geophysical surveys, soil and rock chip sampling programs, field mapping, historical data compilation, and regional reconnaissance at the Mine site. All of these efforts are designed to improve the understanding of the known mineralization, as well as provide data for further exploration of the greater property position.

1.7Data Verification

The pre-2000 drilling data at Hycroft has no historical quality assurance and quality control (QA/QC) information to support it. The post-2005 drilling data (no drilling in 2000 to 2004) has QA/QC information that is sufficient but not best practice. Hycroft has begun to implement best practices for data collection and QAQC in 2021 and will continue to improve those procedures in the future. Hycroft has a history where Au fire assays collected prior to 2000 were factored upward in order to better correlate with blast hole assay results pre-2000. That factor process has been removed from the database for application to this mineral resource. The basis for the removal is discussed later in section 9.1.5.

1.8Metallurgical Testwork

Previous Hycroft metallurgical test programs conducted on the Hycroft deposit consisted of a series of comminution, flotation, concentrate oxidation, and cyanide leaching tests on mineralized materials, flotation tails, and oxidized concentrate of sulfide mineralized materials. Samples for metallurgical testwork were mostly derived from drilled core samples selected to represent the materials from the five main mineralization domains. Testwork was conducted by G&T Kamloops Laboratories (G&T) and SGS Mineral Services, Lakefield (SGS), both in Canada, and by Hazen Research Inc. (Hazen) in Colorado. POX testwork was performed by Kappes, Cassiday & Associates (KCA), SGS and Hazen.

Comminution testwork demonstrate the Hycroft rock mineralization exhibits very high rock competency both in the SAG and ball mills.

Flotation testwork can be summarized as follows:

•Au recoveries from flotation at grinds ranging from 100 to 150 microns were 80% but tended to decrease with grinds finer than 100 microns or coarser than 150 microns;

•Flotation tests performed at neutral pH generally outperformed tests conducted at basic pH;

•Testwork using various frother and promoter reagents were conducted to optimize flotation results; and

•An average mass pull of 13.8% was observed for some tests. The same set of tests indicated a flotation time of 19 minutes for gold and 17 minutes for silver to achieve ~ 80% target recoveries for both.

Oxidation testwork on Hycroft concentrates from the aforementioned flotation testwork included pressure oxidation (POX), roasting, ambient pressure alkaline oxidation and other oxidation methods including chlorination, fine grinding with intense cyanidation, and the Albion process. The following is a summary of the results of the predominant testwork studies conducted.

Results from acid POX testwork on rougher concentrate showed percent Au and Ag recoveries in the mid-90s and 80s, respectively under the following autoclave operating conditions: temperatures between 374°F to 437°F; 100 psi oxygen overpressure; and 60 minutes’ residence time provided the POX discharge material was lime boiled prior to cyanide leaching. Test work from alkaline POX was limited in scope to 10 total samples and showed similar percent recoveries for Au but Ag recoveries were much lower.

Roaster testwork was conducted in 2011 on the Brimstone concentrate from a pilot plant to determine optimum conditions for processing. The results indicate that optimum roast temperatures are between 797°F and 842°F with average recoveries of 89% Au and 74% Ag.


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Results from early batch testwork conducted in 2009 results were positive and indicated that Hycroft concentrates were amenable to oxidation under atmospheric conditions, using trona to create the appropriate alkaline environment to promote oxidation. Pilot plant testing on Hycroft’s three main domains confirmed the findings of the batch tests. Different material types oxidized at varying rates, with Vortex materials oxidizing the fastest followed by Central and then Brimstone. The Master Composite oxidation rate was comparable to Brimstone. At 60% sulfide oxidation, 85% Au and 80-84% Ag recoveries were achievable by atmospheric oxidation for all material types tested.

The viability of the alkaline atmospheric oxidation (AAO) process using trona was demonstrated with a 10-ton per day demonstration plant operated at site from 2016 to 2017. This plant included primary grinding, followed by flotation, atmospheric oxidation, cyanide leaching, countercurrent decantation (CCD) and precipitation. The results indicated Au recoveries peaked at 80% and Ag recoveries were at 90% for the Brimstone mineralized materials.

POX was evaluated in the development of the mineral resource, in part, due to the consistency of sulfide oxidation at elevated pressure and the observation of improved overall gold and silver recoveries.

1.9Mineral Resource Estimation

Mineral resources were developed based on a conventional computer-based block model of the deposit and the application of open pit optimization software to determine the mineralization with reasonable expectation of economic extraction.

Each block was evaluated to determine which process provides the best net return after operating cost. The two processes identified were:

•Run-of-Mine (ROM) cyanide heap leaching of oxide ore; and

•Milling, Flotation, POX followed by Cyanide Leach and Merrill-Crowe.

Mineral resources were based on metal prices of $1,800/troy oz Au and $23.00/troy oz Ag. Mineral resources were contained within a computer-generated optimized pit. Total material in that pit is 3.516 billion tons.

Table 1-1 summarizes the Mineral Resource. The risks to the Mineral Resource are project costs and project recoveries as well as metal prices that can have a substantial impact on the Mineral Resource both positively and negatively.

Mineral resources are not mineral reserves and detailed economic considerations have not been applied. Modifying factors for mine and process design have not been applied.

The Mineral Resource on Table 1-1 represents the total amount of material in the ground that meets the requirements for Mineral Resource.


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Table 1-1: Hycroft Mineral Resources as of February 18, 2022


Classification	Cutoff Grade $ Net of Process	Approximate Cutoff, AuEq	Ktons	Grades		Sulfide Sulfur	Contained Ounces (000)
		oz/ton		Au oz/ton	Ag oz/ton	%	Au	Ag
Heap Leach Resource
Measured	$0.01	0.003	97,086	0.008	0.30	2.75	777	29,417
Indicated	$0.01	0.003	36,046	0.007	0.29	2.10	252	10,417
Meas + Ind	$0.01	0.003	133,132	0.008	0.30	2.57	1,029	39,834
Inferred	$0.01	0.003	101,314	0.008	0.09	1.77	811	9,118

Mill, Flotation Concentrate, POX and Cyanide Leach Process Plant
Measured	$0.01	0.011	372,226	0.013	0.65	1.86	4,839	240,830
Indicated	$0.01	0.011	314,866	0.012	0.53	1.65	3,778	165,305
Meas + Ind	$0.01	0.011	687,092	0.013	0.59	1.76	8,617	406,135
Inferred	$0.01	0.011	349,659	0.012	0.40	1.19	4,196	141,262

Combined Mineral Resources Leach Plus Process Plant
Measured	$0.01	0.003 - 0.011	469,312	0.012	0.58	2.04	5,616	270,247
Indicated	$0.01	0.003 - 0.011	350,912	0.011	0.50	1.70	4,030	175,722
Meas + Ind	$0.01	0.003 - 0.011	820,224	0.012	0.54	1.90	9,646	445,969
Inferred	$0.01	0.003 - 0.011	450,973	0.011	0.33	1.32	5,007	150,380

Notes:

Mineral resources based on metal prices of $1,800/troy oz Au and $23.00/troy oz Ag.

Cutoffs are income – process cost = NPR = NSR – Process OpEx.

Numbers may not match exactly due to rounding.

Mineral resources are contained within a computer-generated optimized pit. Total material in that pit is 3.516 billion tons.

All units are imperial, except for troy ounces for Au and Ag. Ktons means 1,000 short tons of 2,000 lbs. Au and Ag grades are in troy ounces / short ton.

The mineral resources statement is based on Hycroft being mined as a conventional hard rock open pit mine producing sulfidic ore to a mill+pressure oxidation of concentrate processing plant and ROM oxide ore to a leach pad.

1.10Conclusions

IMC developed the Hycroft deposit block model based on 2,482,722 ft of drilling from 5,323 drillholes.

Previous Hycroft metallurgical test programs conducted on the Hycroft sulfide deposit consisted of a series of comminution, flotation, concentrate oxidation, and cyanide leaching tests on mineralized materials, flotation tailings, and oxidized sulfide concentrates.

Comminution testwork demonstrates the Hycroft rock mineralization exhibits very high rock competency. Flotation at grinds ranging from 100 to 150 microns at neutral pH with strong non-selective sulfide collectors showed Au and Ag recoveries. AAO using trona, showed promise reaching 60% sulfide oxidation with 85% Au and between 80-84% Ag recoveries. Further oxidation testwork on Hycroft concentrates from the aforementioned flotation testwork improved recoveries with POX results in the mid-90s and 80s for Au and Ag, respectively. Test work from alkaline POX was limited in scope to ten total samples and would require significant additional testing for project development.

Likewise, roaster testwork requires additional testing for project development as few of the tests were performed. Average recoveries from roaster tests were 89% Au and 74% Ag.


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The mineral resources statement was developed using a conventional computer-based block model. Each block was evaluated to determine the net return from the following two processes:

• ROM cyanide heap leaching of oxide ore; and

• Milling, Flotation, POX followed by Cyanide Leach and Merrill-Crowe.

1.11Recommendations

The QPs recommend Hycroft proceed with a further study to develop a process plant to treat sulfide ore in addition to its oxide heap leaching capability provided it confirms the basis of the pre-2000 Au assays, update and improves the interpretation of the fault boundaries, major rock types, and alteration, and specifically drill cores to target areas within the mine plan that are not well-defined and update the slope stability.

The QPs also recommend additional testwork focusing on optimizing grind size and mass pull percentage, flotation reagent suite, POX, equipment sizing, residence times, lime/limestone and oxygen consumption. Also recommended is that Hycroft obtain solid separation data and flocculant requirements, optimize cyanide consumption and reagent use in cyanide destruction.


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2INTRODUCTION

2.1Overview

This Technical Report Summary summarizes the results of an Initial Assessment and supports the disclosure of mineral resources at the Mine located in northwestern Nevada. The work has been prepared at the request of Hycroft Mining Holding Corporation (Hycroft). The report follows the requirements and outline as described in the U.S. Securities and Exchange Commission ruling S-K Subpart 1300 (S-K1300). This mineral resource estimate has been completed by Ausenco Engineering USA South Inc. (Ausenco), Independent Mining Consultants, Inc. (IMC), and WestLand Engineering & Environmental Services, Inc. (Westland). Employees of IMC and Ausenco who have worked on and approved this mineral resource estimate are Qualified Persons as defined in SK-1300.

There are three major changes to the Project that have necessitated an update to the statement of mineral resources:

1) An updated understanding of the mineral processing options including new processing costs, percent recoveries and associated assumptions;

2) Corrections and updates to the drillhole database; and

3) Updates to the geologic and grade interpretation.

This Technical Report Summary supersedes all previous technical studies, including the last statement of mineral resources with an effective date of July 31, 2019.

The mineral resource is based on information provided by Hycroft which has been checked and validated wherever possible by IMC. The calculations and interpretations presented here are the work of IMC, who takes responsibility for the published mineral resource.

Some sections of this report were published previously as part of the previous Technical Reports and are listed below in Section 2.6. The sections of these reports which were utilized have been reviewed by both IMC and Ausenco in sufficient detail so that Qualified Persons at IMC and Ausenco have assumed responsibility for this work.

Hycroft staff have provided all requested information and have worked with IMC and Ausenco in an open and transparent manner throughout the Project period.

This report uses imperial units including troy ounces for gold and silver, throughout. Occasional use of non-imperial units will be clearly noted and explained in text when they occur. Tons means short tons of 2000 lbs. Ktons means 1000 short tons. Precious metal grades are presented in units of troy ounces per short ton (oz/ton).

2.2Qualified Persons

Below is a list of the firms that acted as Qualified Persons (QPs) in the preparation of this Technical Report Summary:

•Ausenco Engineering South USA, Inc. is responsible for sections 1.1, 1.2, 1.3, 1.5, 1.8, 1.10, 1.11, 2, 3.1, 3.2, 3.3, 3.4, 3.5, 3.7, 3.8, 4, 5, 10, 21, 23.1, 23.3, and portions of sections 22, 24, and 25.

•Independent Mining Consultants, Inc. is responsible for sections 1.4, 1.6, 1.7, 1.9, 6, 7, 8, 9, 11, 20, 23.2, and for portions of sections 22, 24, and 25.

•WestLand Engineering & Environmental Services, Inc. is responsible for subsection 3.6.

2.3Site Visits

Ausenco field experts completed a site visit of the Hycroft property on April 8, 2021 to inspect the existing infrastructure.

IMC Qualified Persons, John Marek P.E. and Anh D. Nguyen, P.E. visited the Hycroft property on August 5, 2021. Their purpose was to review the existing core and logs.

2.4Effective Dates

The overall Report effective date is taken to be the date of the updated mineral resource estimate is February 18, 2022.


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2.5Sources of Information and References

The authors sourced information from documents listed in the References section of this report (Section 24).

2.6Previous Technical Report

Hycroft Mining Holding Corporation previously filed the following Technical Report Summary:

•Newman, S., DeLong, R.F., Clarkson, B. M., Carew, T., Hartmann, M., Technical Report Summary: Heap Leaching Feasibility Study. Prepared by M3 for Hycroft Mining Corporation, Effective date: July 31, 2019.

Hycroft Mining Corporation previously completed the following Technical Report that was prepared in accordance Canada’s National Instrument 43-101 Standards of Disclosure for Mineral Projects:

•Ibrado, A.S., Roth, D.K., Snider, J.W., Brown, R.A., Harris, D.A., Pennstrom, W.J., Peterson, A.T. NI 43-101Technical Report Mill Expansion Feasibility Study, Winnemucca, Nevada, USA. Prepared by M3 for Allied Nevada Gold Corp., Effective date: November 03, 2014.


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2.7Units and Abbreviations

Table 2-1: Unit Abbreviations


Unit			Description
ac			acre
asl			above sea level
Axb			Hardness of ore in term of impact breakage, unitless
B			billion
Btons			billion short tons
bgs			below ground surface
°C			Celsius
D			day
°F			Fahrenheit
fasl			feet above sea level
ft			feet
G			gravity
g			gallon
gpm			gallons per minute
g/y			gallons per year
Hp			horsepower
in.			inch
Kg.			kilogram
ktons			kilo short tons
kV			kilovolt
lb			pound
M			million
mi			mile
mi2			square mile
Mm			millimeters
Mtons			million short tons
Min.			minute
Moz			Million ounces
oz			ounce
oz/ton			ounces per short ton
oz/g			ounces per gallon
pcf			pounds per cubic foot
ppm			parts per million
psig			gauge pressure
ton			short ton
ton/d			short tons per day
US$			United States dollars
wt/wt			weight percent
%			percent


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Table 2-2: Name Abbreviations


Name			Description
AAO			Atmospheric alkaline oxidation
Ag			silver
Au			gold
Ausenco			Ausenco Engineering USA South, Inc.
BLM			Bureau of Land Management
BMRR			Bureau of Mining Regulation and Reclamation
CCD			Countercurrent decantation
CFR			Code of Federal Regulations
CS			Carbon Steel
Duval			Duval Corporation
EA			Environmental Assessment
EIS			Environmental Impact Statement
EMS			EM Strategies
G&T			G&T Kamloops Laboratories
Golder			Golder Associates USA Inc., a member of WSP
Hazen			Hazen Research Inc.
Hycroft			Hycroft Mining Holding Corporation
ICP			Inductively coupled Plasma
IMC			Independent Mining Consultants, Inc.
KCA			Kappes, Cassiday & Associates
LECO			Laboratory Equipment Corporation
LOM			Life of Mine
Mill+ConcPOX			pressure oxidation treatment of the concentrates
MSHA			Mine Safety and Health Administration
MWWAI			Michael W. West and Associates Inc
NaHS			Sodium hydrosulfide
NAC			Nevada Administrative Code
NaCN			Sodium cyanide
NDEP			Nevada Department of Environmental Protection
NDOW			Nevada Department of Wildlife
NDWR			Nevada Division of Water Resources
NEPA			National Environmental Policy Act
NHLF			North Heap Leach Facility
NPI			Net Profits Interest
NPR			Net of Process
NRP			Nevada Reclamation Permit
PAX			Potassium amyl xanthate
POX			Pressure oxidation
QA/QC			Quality Assurance and Quality Control
RC			Reverse circulation
ROD			Record of Decision
ROM			run-of-mine
ROW			right-of-way
SEC			United States Securities and Exchange Commission’s


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SEIS			Supplemental Environmental Impact Statement
SGS			SGS Minerals Service Lakefield
SK1300			U.S. Securities and Exchange Commission ruling S-K Subpart 1300
SRK			SRK Consulting (U.S.), Inc.
Tcm			The camel conglomerate
TMF			Tailings Management Facility
TRIFR			Total Reportable Incident Frequency Rate
TSG			Tertiary Sulfur Group
USFWS			United States Fish and Wildlife Service
QPs			Qualified Persons
WestLand			WestLand Engineering & Environmental Services, Inc.
Vista			Vista Gold Corporation


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3PROPERTY DESCRIPTION AND LOCATION

3.1Introduction

The Mine property is an existing gold and silver operation located 54 miles west of Winnemucca in Humboldt County and Pershing County, Nevada, as shown in Figure 3-1. The Mine property is accessible via Nevada State Route 49 (Jungo Road), an all-weather, unpaved road that is maintained by Humboldt County and Hycroft. A major east–west railway runs immediately adjacent to the property.

The Mine property straddles Townships 34, 35, 35½ and 36 North and Ranges 28, 29 and 30 East (MDB&M) with an approximate latitude 40°52’ north and longitude 118°41’ west. The mine is situated on the western flank of the Kamma Mountains on the eastern edge of the Black Rock Desert.

The Mine property consists of 30 private parcels with patented claims that comprise approximately 1,912 acres, and 3,247 unpatented mining claims that encompass approximately 68,759 acres. The combined patented and unpatented claims comprise approximately 70,671 acres. The mining claims are comprised of two primary properties, Crofoot and Lewis. The Crofoot and Lewis properties together include approximately 11,829 acres. The Crofoot property covers approximately 3,500 acres and is virtually surrounded by the 8,400 acres of the Lewis property.

Existing facilities on site include two administration buildings, a mobile maintenance shop, a light vehicle maintenance shop, a warehouse, three (3) Heap Leach Pads – Crofoot, North, and Brimstone, primary, secondary and tertiary crushing systems, two Merrill-Crowe process plants and a refinery. It is considered that existing components of the mine property would be utilized for future development. The Mine operates under permit authorizations from the BLM, NDEP, NDOW, NDWR and County agencies. At the date of this report, the company had approximately 80 employees at the mine.


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Figure 3-1: Hycroft Mine Property Location Map

Source: Figure adapted from Hycroft, 2022


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3.2Property Ownership and Title In (Jurisdiction)

The mine is owned and managed by Hycroft Resources and Development, LLC, a wholly owned subsidiary of Hycroft Mining Holding Corporation.

3.3Land Status

Hycroft holds 3,247 unpatented mining claims, comprising 68,759 acres, located as follows:

•T36N, R29E, Sections: 28, 32, 33

•T36N, R30E, Sections: 19, 28-34

•T35 1/2N, R29E, Sections: 25, 26, 35, 36

•T35N, R29E, Sections: 1-3, 10-15, 21-28, 31-36

•T35N, R30E, Sections: 2-10, 15-23, 25-36

•T34N, R28E, Sections: 1, 2, 11, 12, 13

•T34N, R29E, Sections: 1-28, 33

•T34N, R30E, Sections: 2-11, 17-20, 29, 30

The company owns 30 private parcels (patented lode and placer claims) comprising 1,912 acres, located as follows:

•T35N, R29E, Sections: 24, 25, 35, 36

•T35N, R30E, Sections: 19, 30, 31

•T34N, R29E, Sections: 1, 2

Combining the patented and unpatented claims, Hycroft claims total approximately 70,671 acres and are depicted in Figure 3-2. Individual mining claims for each township range and section are presented in Appendix 1. Ausenco has defined the project centroid in the following mine grid coordinates:

•51 500 N

•20 500 E

This point is located central to all mine facilities. The project centroid shall be used to reference all other locations within 1 mile.

Much of the project area is located on un-surveyed public and private land for which the sections, ranges, and townships listed above have been interpolated. Patented claims have been surveyed (Wilson, 2008; Prenn, 2006). The following is a list of land acquisitions/transactions made over the years which constitute the entire Hycroft land claim package: has been assembled through a series of transactions:

•The Crofoot property and approximately 3,500 acres of claims were acquired by Vista in 1985.

•The Crofoot property, originally held under lease, is owned by Hycroft subject to a 4% Net Profits Interest (NPI) retained by the former owners, capped at total future payments of US$7.6 M.

•The Lewis property and approximately 8,700 acres of claims were acquired by Vista in early 1987.

•In 2006, approximately 13,100 acres of additional claims were staked by Vista. These claims are contiguous or proximate to the original Crofoot and Lewis claims.

From 2008 through end of October 2014, approximately 45,371 acres of additional claims were staked by Hycroft contiguous to the existing Hycroft claims.


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Figure 3-2: Hycroft Mine Claims Map

Source: Figure prepared by Hycroft, October 2021.


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Payment of annual claim holding fees to the BLM and Humboldt and Pershing Counties are made every third quarter (Q3). Payments are current through the 2020-2021 claim years, with US$589,944 paid in Q3 2021. Payment of annual land holding fees and taxes is required to continue to hold the Hycroft property in good standing.

Hycroft controls all surface and mineral rights within the Hycroft mineral resource area. No further land acquisition is required for operation of the mine and processing facilities as presently designed.

Figure 3-3 shows the property layout including site facilities, mine workings, leach pads and waste dumps.

Figure 3-3: Current Property and Facilities Layout (2021)

Source: Figure prepared by Hycroft, 2022.


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3.4Property Agreements and Royalties

The original owners of the Crofoot property have a retainer of 4% NPI. In 1996, the lease/purchase agreement was amended to provide for minimum advance royalty payments of US$120,000 on January 1 of each year in which mining occurs on patented and unpatented claims. The sum of payments for the Crofoot property is capped at US$7.6 M, of which US$3.0 M has been paid through December 2021. An additional $120,000 annually is due if ore production exceeds 5 Mtons from the Crofoot property on either patented or unpatented claims in any calendar year. All advanced royalty payments are taken as a credit against the 4% NPI. Table 3-1 shows the royalty amount and other annual land holding costs.

Table 3-1: Hycroft Annual Land Holding Costs


Month Due	Lessor	Type	Amount
Jan., Apr., Jul., & Oct.	Crofoot1	Advance Royalty	US$120,000
Monthly	Sprott Royalty	Net Smelter Return Royalty	1.5% NSR
August-October	U.S. BLM, Humboldt & Pershing Counties	Claim Fees	US$589,944

1 The Crofoot royalty is a minimum of $120,000 due in January but is only payable if mining occurs.

2 The Sprott royalty is equal to 1.5% of Net Smelter Returns free and clear of withholding taxes or similar taxes.

3.5Water Rights

Hycroft controls a total of 13 separate water right permits administered by the NDWR. These permits are held in ownership either by Hycroft, or by other private parties and leased to Hycroft. Water resources to support the Mine are controlled under 11 permits in the Black Rock Desert Basin totaling 21, 457.95 acre feet per year (6.99 billion gallons per year). Two of these water permits are outside the Black Rock Desert Hydrographic Basin and used to support construction maintenance of Jungo Road with Humboldt County.

3.6Liabilities & Encumbrances

The consolidated financial statements of Hycroft Mining Holding Corporation set forth its material liabilities as of the date of such financial statements. The assets of Hycroft Mining Holding Corporation and its subsidiaries (collectively, the “Company”) are subject to encumbrances and obligations, including encumbrances and obligations under and associated with the (i) the Amended and Restated Credit Agreement dated as of May 29, 2020 by and between the Company and Sprott Private Resource Lending Corp. and certain of its affiliates; (ii) the Sprott Royalty Agreement dated May 29, 2020 by and between the Company and Sprott Private Resource Lending II (Co) Inc.; (iii) the subordinated debt issued under the Omnibus Amendment to Note Purchase Agreement and Exchange Agreement dated as of May 28, 2020 by and among the Company and the subordinated debt holders; and (iv) royalty payment obligations associated with the Crofoot claims.

3.6.1Environmental Liabilities

Gold production began on the property in 1983 and continued through 1985 when Standard Slag opened the Lewis Mine. There was a brief gap in mining until Hycroft acquired the Lewis Mine and the Crofoot claims and recommenced mining in 1988. Mining operations continued until 1998 when mining was placed on standby due to low metal prices. Process operations continued until 2004 when the property was placed on care and maintenance.

Efforts began in 2003 to update the Reclamation Plan, associated cost estimate, and related amount of surety bond posted with the BLM. During the years December 31, 2011 and 2012, Hycroft increased collateral account balances to support additional surety bonds for the benefit of the BLM. These additional surety bonds allowed Hycroft to continue operations at the Mine and to expand exploration activities outside of the Mine. In 2011, Hycroft received a reimbursement of US$0.5M related to reclamation costs that had been paid out.

In January 2014, the BLM approved an updated reclamation cost estimate allowing for the phased bonding of the expansion activities. The required bond amount was lowered from US$63 M to US$58.3 M. Hycroft has entered into Surface Management Surety Bonds with insurance companies that meet the financial requirements of the BLM to comply with the total requirement of US$58.3 M as detailed in the September 2013 reclamation cost estimate that requested the phasing of the mill expansion activities. Additionally, Hycroft has posted an exploration bond with the BLM in the amount of US$1.0 M.


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3.6.2Mine Safety Disclosures

The operation of the Mine is subject to regulation by the Federal Mine Safety and Health Administration (MSHA) under the Federal Mine Safety and Health Act of 1977 (the Mine Act). MSHA inspects the Mine on a regular basis and issues various citations and orders when it believes a violation has occurred under the Mine Act. In 2021, MSHA issued forty-one (41) citations and five (5) of those were “Significant and Substantial" Violations under §104(a) citations. The citations were issued to Hycroft, but a majority of those were issued to the contractors. Nevertheless, fines totaled over US$30,000 including citations and orders issued to contractors. In 2020, MSHA issued eighty-nine (89) citations; of those, twenty-five (25) were “Significant and Substantial" Violations Under §104(a) totaling over US$30,000, including citations and orders issued to contractors. The proposed assessments as of and for the year ended December 31, 2021, were taken from the MSHA Mine Data Retrieval System.

Hycroft mandated mine safety and health programs include employee and contractor training, risk management, workplace inspection, emergency response, accident investigation, and program auditing with a goal to have zero workplace injuries and occupational illness. The Mine’s Total Reportable Injury Frequency Rate per 200,000 man-hours worked including contractors (TRIFR) was 0.64 on December 31, 2021. On December 31, 2020, the Mine’s TRIFR was 2.30.

3.6.3Operating Permits

The Mine operates under permit authorizations from the BLM, NDEP, NDOW, and NDWR. All operating and environmental permits, approved by the BLM, NDEP, NDOW and NDWR, are in good standing for mining operations at the Mine. Table 3-2 summarizes the operating permits while Table 3-3 shows the miscellaneous permits for the property.

Table 3-2: Hycroft Operating Permits


Operating Permits	Issuing Agency	Number	Status
Plan of Operations	BLM	NVN-064641	Current
Mercury Operating Permit to Construct	NDEP - BAPC	AP1041-2255	Current
Class I Air Quality Operating Permit to Construct	NDEP - BAPC	AP1041-2974	Current
Class I Air Quality Operating Permit to Construct	NDEP - BAPC	AP1041-3344	Current
Class I Air Quality Operating Permit to Construct	NDEP - BAPC	AP1041-3269	Current
Permit to Operate a Public Water System	NDEP - BSDW	HU-0864-12NTNC	Current
Class II Air Quality Permit	NDEP - BAPC	AP1041-0334.05	Current
Water Pollution Control Permit-Crofoot Project	NDEP - BMRR	NEV60013	Current
Water Pollution Control Permit-Brimstone Project	NDEP - BMRR	NEV94114	Current (Application Shield)
Bioremediation Facility Permit	NDEP - BMRR	GNV041995-HGP15	Superseded by Water Pollution Control Permit
Reclamation Permit	NDEP - BMRR	134	Current
Mining General Stormwater Pollution Prevention Permit	NDEP - BWPC	R300000: MSW-177	Current
Class III Landfill Waiver	NDEP - BSMM	F-346	Current
Artificial Pond Permit (Brimstone Process Ponds)	NDOW	S34481	Current
Artificial Pond Permit (Crofoot Process Ponds)	NDOW	S36665	Current
Artificial Pond Permit (North Process Ponds)	NDOW	S36661	Current
General Onsite Sewage Disposal System	NDEP - BWPC	GNEVOSDS09	Current
Septic Onsite Disposal	NDEP - BWPC	GNEVOSD09L-00418	Current
Dam Safety Permit (Crofoot Process Ponds)	NDWR	J-273	Current
Hazardous Materials Storage Permit	NV State Fire Marshall	8250	Current
Special Use Permit	Pershing County	SUP 12-04	Current
Special Use Permit	Humboldt County	UH-12-04	Current


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Table 3-3: Hycroft Miscellaneous Permits


Operating Permits	Issuing Agency	Number	Status
Microwave Repeater; Sec. 29, 30	BLM	NVN46292	Current
ROW Wells/Pipeline/Power Line; Sec. 3	BLM	NVN46564	Current
ROW 2 Wells/Pipeline/Power Line	BLM	NVN46959	In renewal
ROW Road & Waterline (Old Man camp to Lewis)	BLM	NVN39119	In renewal
ROW Crofoot pipeline	BLM	NVN44999	In renewal
ROW 24 kV Aerial Powerline, Lewis/Floka	BLM	NVN54893	Current
Kamma Peak Station	FCC	WNER344	Current
Sulfur Mine Station	FCC	WNER345	Current
Winnemucca Mountain Station	FCC	WNER346	Current
Base Station & 45 Mobile Units	FCC	WNKK336	Current

Operating and miscellaneous permits that require annual maintenance fees are shown in Table 3-4. Fixed annual fees are required for storm water and public drinking water system permits based upon the current Nevada regulatory structure. The other annual fees are based on annual mining production, quantities and types of chemicals stored on site, existing and permitted surface disturbance, and the level of actual and permitted air emissions. The variable fees shown are based upon the 2021 operational conditions.

Table 3-4: Hycroft Permits and Annual Fees


Permit and Fee Description			Annual Amount (US$)
Air Quality Operating Permit AP1041-0334.052			$3,312
Air Quality Operating Permit AP1041-2255			$14,401
Air Quality Operating Permit AP1041-2974			$22,082
Air Quality Operating Permit AP1041-3344			$14
Reclamation Permit			$30,000
Nevada Radioactive Material License			$1,100
Stormwater Permit			$200
Artificial Pond Permit			$8,750
Water Pollution Control Permit NEV94114			$20,000
Water Pollution Control Permit NEV60013			$20,000
State Fire Marshall			$150
Public Drinking Water System			$225
Septic System Permits			$600
Toxic Release Inventory Annual Fee			$3,000
Nevada LP-Gas License			$450
TOTAL			$124,284

Hycroft currently holds six ROW leases and two exploration notices with the BLM, as described in Table 3-5 along with fees and renewals.


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Table 3-5: Right-of-Way Payment and Renewal Schedule


ROW Number	Annual Payment Amount (estimated)	Payment Date	Expiration Date
NVN46292	$125	01/01/22	12/31/2048
NVN46564	$100	01/01/22	12/31/2046
NVN46959	$600	01/01/22	01/01/2023
NVN39119	$400	01/01/22	01/01/2023
NVN44999	$300	01/01/22	01/01/2023
NVN54893	$200	01/01/22	10/10/2025

3.6.4Hycroft Expansion Permitting and Timelines

Hycroft submitted a Plan of Operations for an expansion of its heap leach facilities, open pits and waste rock facilities to the BLM in April 2010. A major modification to the State Water Pollution Control Permit was submitted in 2011 for the process components that included engineering design reports from Golder Associates. The permit modification was issued in August 2012. An amended Plan of Operations that included a rail spur, open pit expansion and processing complex was submitted to the BLM in August 2012. The BLM determined that an Environmental Assessment (EA) was required, deemed the Plan of Operations complete, and initiated public scoping in December 2012. In March 2013, NV Energy submitted a ROW application for the power line associated with the Hycroft Mill. The BLM determined that this action should be analyzed with the Hycroft EA. Approval was received in December 2014. The permits required to construct and operate the crushing system and to begin mill construction were received in 2012. The air quality permit for operation of a mill was submitted in December 2012 and issuance was received in late 2013.

The Plan of Operations for a rail spur, open pit expansion and processing complex, that included a TMF and expanded Heap Leach Facility, was completed in December 2014, with the BLM issuance of the Record of Decision authorizing the proposed action received in January 2015. A major modification to the State Water Pollution Control Permit was submitted in 2011 for the process components that included engineering design reports from Golder Associates. The permit modification was issued in August 2012. All other permits required for the heap leach expansion have been received.

A Plan of Operations for the proposed southeast location of TMF, mining below the water table and expanded facilities was submitted to the BLM in April 2014. The BLM determined that a Supplemental Environmental Impact Statement (SEIS) was required. In October 2019, the BLM issued a record of decision on the SEIS permitting the new TMF location, expanded facilities and deeper pit depths.

In December 2010, Hycroft submitted a minor modification to the NDEP which proposed increasing the permitted processing rate from 10 Mtons per year to 12 Mtons per year. This modification was approved in February 2011. In May 2011, Hycroft proposed a major modification to build a new heap leach pad on the site of the closed Lewis pad and to increase the processing rate to 30 Mtons/y. This modification was approved by the NDEP in December 2011. In January of 2012, Hycroft submitted another major modification to construct a heap leach facility on the south extent of the property. The facility was referred to as the South Heap Leach Facility (SHLF). Around the same time, Hycroft submitted a modification proposing to add both a north and south processing area, increasing the Brimstone and Lewis Heap Leach Pads permitted height to 400 ft, and increasing the permitted processing rate to 36 Mtons of ore per year. Both modifications were approved by the NDEP in September 2012. Later, in December 2012, Hycroft submitted a minor modification proposing to add a Merrill-Crowe facility at the North Process Area. NDEP approved this modification in May 2013. In March of 2013, Hycroft submitted another modification to construct a combined heap leach and tailings storage facility, referred to as the South Processing Complex (SPC), in the same location as the previously permitted SHLF. The SPC uses the new SHLF, constructed in a horseshoe shape, to provide the embankment for the Southeast TMF located in the central portion of the new SHLF. Also, as part of this modification, Hycroft proposed the construction of a mill and related facilities for processing high-grade ore at an approximate throughput of 65,000 tons per day (ton/d) during Phase 1 to a final phase capacity of 132,000 ton/d. Tailings were proposed to be pumped to the TMF at the South Processing Complex. These 2013 major modifications were approved by the NDEP until August 2017.

In September 2014, Hycroft submitted a minor modification to expand the Brimstone-North Heap Leach Facility to the southeast by approximately 80 acres including an additional Event Pond at the existing North Area Merrill-Crowe facility. NDEP approved these minor modifications in March 2015.


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In April 2019, Hycroft submitted a major modification to construct a new heap leach facility named Hycroft Heap Leach Facility Stage 1 (Stage 1 HLF) north of the North Processing Facility. The Stage 1 HLF will have a storage volume of 29 Mtons and is the first stage of the larger facility (Hycroft HLF) with a storage capacity of 550 Mtons. The ultimate footprint of the Hycroft HLF will cover approximately 925 acres, the Stage 1 footprint is approximately 390 acres including the ponds, channels, and roads. Of this area, 234 acres will be geomembrane lined, with the HLF pad comprising 204 of these acres. Pregnant solution collected from the pad will be pumped to the existing North Merrill-Crowe process facility for precious metals recovery. The Barren solution from the North Merrill-Crowe facility will then be returned to the top of each lift and applied over a designated cell area using a drip and sprinkler system. The major modification was approved by NDEP in July 2020.

Currently, Hycroft has all permits required to restart the Mine and recently received the Federal Record of Decision for the Phase II Environmental Impact Statement supporting the LOM pit development.

•Received Record of Decision from BLM for EIS (10-22-19):

◦Current operating plan is fully permitted.

◦Existing operating permits will be amended as new facilities/infrastructure are required.

◦EIS allow for flexibility:

▪Expanded pits.

▪Construction of a tailings management facility to the south of the property, if needed.

•Phase 1 of the new leach pad is permitted.

•Phase 1A of the new leach pad is constructed and will complete electrical when needed, but not expected before late 2022.

•Phase 1B of the new leach pad and future phases will be planned for construction from cash flows when needed.

Any future expansion activities recommended in this Technical Report Summary will require multiple federal, state and local permits. The U.S. Fish and Wildlife Service (USFWS)will require modification to the Golden Eagle Take Permit for the NE TMF and extensions of the South (Vortex) Dump.

3.6.5Crofoot Heap Leach Facility Closure

NDEP approved activities associated with the closure of the Crofoot processing facilities and ponds submitted under an updated Final Permanent Closure Plan in November 2017 and the Crofoot processing facilities permitted in Water Pollution Control Permit NEV60013. Facilities that closed under this plan included the Crofoot heap leach pad and associated processing components. Construction of a drain-down collection system was completed in 2012. Although regrading of the Crofoot heap leach pad was initiated in 2017, there remains significant earthworks, grading and growth medium application, yet to be completed before the pad can be closed.

3.7Environmental Considerations

The Hycroft area has been surveyed for surface water resources, including Waters of the United States, biological resources, cultural resources, and groundwater resources. The Golden Eagle (Aquila chrysaetos) is known to occur adjacent to the Hycroft Project. Hycroft is working with the BLM and the USFWS on the management of this species.

3.8Social License Considerations

Social and community impacts have been and are being considered and evaluated in the NEPA process. Potentially affected Native American tribes, tribal organizations, and/or individuals are consulted during the preparation of all plan amendments to advise on proposed projects that may have an effect on cultural sites, resources, and traditional activities. Potential community impacts to existing population and demographics, income, employment, economy, public finance, housing, community facilities, and community services are also evaluated during NEPA review processes. There are currently no social or community issues that materially impact Hycroft’s ability to extract mineral resources.


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4ACCESSIBILITY, CLIMATE, LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY

4.1Access

The Mine and its related facilities are located 54 miles west of Winnemucca, Nevada along State Road No. 49 (Jungo Road), a good quality, unpaved road. Access is also possible from Gerlach via Jungo Road, Imlay or Lovelock by dirt roads intersecting Interstate 80. Winnemucca is a commercial community on Interstate 80 where a majority of the Mine’s employees are likely to reside. Winnemucca is 164 miles northeast of Reno, Nevada. The town is served by a transcontinental railroad and has a small public airport and there are adequate room, boarding and dining facilities.

4.2Climate

The climate at the Mine is classified as arid, with an average precipitation of 7.7 inches per year; most of which occurs during the winter and spring months. Winds are generally light with an occasional dust or sandstorm, particularly in the spring.

Temperatures are moderate during the summer ranging from 50ºF at night and to above 90ºF during the day. Winter temperatures average 20ºF at night and 40ºF during the day. The average range between the highest and lowest daily temperatures is 30 to 35ºF as a result of strong surface heating during the day and rapid nighttime cooling due to the dry air. The Mine has not reported experiencing major delays in production due to inclement weather and operates year-round.

4.2.1Local Resources and Infrastructure

Existing infrastructure at the Mine consists of the following: a truck shop, a maintenance building, a laboratory, ore crushing facilities, an administration building, and other service-related structures. Power is supplied to the site from nearby power lines that are fed directly from the main power grid and there is a modern communications system including cellular connections. Potable water is sourced from a well located approximately one mile south of the Crofoot Heap. A major east–west railway passes through the Hycroft claim position.

The Mine is in a well-known mining jurisdiction near several towns including Winnemucca, Gerlach and Lovelock. The Mine’s workforce primarily lives in Winnemucca (Humboldt County) and Lovelock (Pershing County).

Initial surveys indicated that the town of Winnemucca has the required infrastructure (short- and long-term rooming and boarding facilities, dining establishments, shopping, emergency services, schools, etc.) to support the maximum workforce and dependents. The Mine has always been successful in filling positions with qualified mining personnel from all over the country.

Currently, the Mine operates three production wells that are located four to five miles west of the mine, and a single potable well. These four production wells are the main sources of water for the mine site. All of the water rights are within the Black Rock Desert Hydrographic Basin, a recently designated basin. Water rights are shown in Table 4-1.

Hycroft controls sufficient land position and water rights to support all of its planned facilities and process water demands.


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Table 4-1: Hycroft Water Wells and Permitted Yearly Consumption


Application No.	Permit Diversion Limit (cfs)	Annual Appropriation Limit (acre-ft)	Point of Division
81228	0.4	14.83	T34N R29E S3
81226	3.2	724.79	T35N R29E S31
81225	3.2	303.43	T35N R29E S31
81227	2.0	1,448	T35N R29E S31
81224	2.0	1,448	T34N R28E S1
81408	5.4	3,890	T35N R29E S31
81409	5.4	3,890	T35N R29E S31
84477	0.3	177.9	T35N R29E S31
82274	10	4,096	T35N R29E S31
82355	3.3	2,050	T35N R29E S31
82356	5.6	3,415	T34N R28E S1
Total	40.8	21,457.95

A fully developed project will include plans to develop access and haul roads to new processing facilities, a tailings management facility, and additional waste rock storage dumps.

Furthermore, the development of a rail spur is recommended off the existing rail line for the receipt of grinding media, fuel, reagents, and other supplies.

A power study is needed to be conducted to upgrade the existing power at the site in the event that a fully developed processing plant is proposed.

4.3Seismicity

In 2012, Michael W. West and Associates Inc. (MWWAI) completed a review of the Hycroft deterministic seismic hazard assessment (DSHA). MWWAI concluded that historical seismicity in the vicinity of the site is low to moderate with no relation to mapped faults. No faults in the project area are classified as “active/capable” based on an unequivocal association of instrumentally recorded earthquakes in the last approximately 50 years. MWWAI stated that a comparison of the USGS national probabilistic seismic hazard model to deterministic and probabilistic floating earthquake PGAs show reasonable agreement. MWWAI recommends the use of the deterministic and probabilistic PGAs presented in the DSHA.


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5HISTORY

5.1Property History

Mining at the Mine began in 1983 with a small heap leach operation known as the Lewis Mine. In 1987, Vista acquired the Lewis Mine and in 1988, they acquired the Crofoot Mine. The Mine was comprised of various open pits on the property (e.g., the Bay, South Central, Boneyard, Gap and Cut-4 pits along the Central Zone and Brimstone) and produced approximately 1.2 Moz of Au and 2.5 Moz of Ag from 1983 to December 1998 when the operations were suspended due to low Au prices at the time (< $300/oz). An additional 58,700 ounces of Au was produced from the leaching and rinsing of the heap leach pads from 1999 through 2004, after the mine had been placed on a care and maintenance program. The remaining leasehold interest in the Lewis property was purchased by Vista in December 2005, in consideration of the US$5.1 M payment, resulting in the elimination of the 5% NSR royalty on Au and 7.5% NSR royalty on Ag.

In May 2007, Vista’s Nevada-based holdings were spun out into Allied Nevada Gold Corp. The Hycroft Mine was included as part of the transfer of ownership allowing Allied Nevada to explore, expand, and further develop the resources at the Mine. In September 2007, Allied Nevada’s Board of Directors approved the reactivation of the Mine, and a year later in December 2008, the Mine had produced its first doré which was shipped to an offsite refinery for final processing, yielding Au and Ag bullion. Permitting to construct a new refinery was received and completed at the Brimstone plant site by June of 2009. By the end of 2009, the Mine was achieving the forecasted ore production capacity. In 2010, the mine began an expansion program which included the construction of a 21,000 gallon per minute Merrill-Crowe processing plant, a three-stage crushing facility and upgrades to their solution pumping capacity. With the construction of the North leach pad complete in 2013, the total leach pad surface area at the Mine had increased to over 20 million square ft including the Brimstone and Lewis leach pads. Active mining ceased again in June 2015 due to low metal prices yet leaching of the mined ore continued through 2018.

On October 22, 2015, Allied Nevada emerged from its financial restructuring and changed its name to Hycroft Mining Corporation.

In late 2018, Hycroft began construction of new pads for demonstration of heap oxidation and leach process in a commercial setting. Additionally, Hycroft began preparing the mine and mining equipment for a restart. Active mining began again in April 2019, from 2019 to November 10, 2021, only oxide ore has been placed on the new leach pads during this time with production of Au and Ag continuing through to present. Transition and sulfide materials, when encountered, during active mining were set aside for future processing.

5.2Mining History

The earliest recorded mining in the Sulfur District, where the Mine is located, began in the late 1800’s following the discovery of significant native sulfur deposits (Couch and Carpenter, 1943; Wilden, 1964). Mining of native sulfur was sporadic from 1900 to 1950 with over 181,488 tons of sulfur ore, grading approximately 20-35% sulfur, mined and milled (McLean, 1991).

In addition to sulfur, high-grade Ag mineralization, consisting of nearly pure seams of cerargyrite (AgCl), was discovered in 1908 at Camel Hill (Vandenburg, 1938). Assays up to 3,439 oz/ton Ag and 0.362 oz/ton Au were reported (Jones, 1921). Ag mining ceased in 1912 with an estimated 165,375 Ag ounces produced. Minor Ag mining also occurred along the East Fault at the Snyder Adit, and Ag samples as high as 66 oz/ton (Friberg, 1980) and 29 oz/ton (Bates, 2001) were reported.

During the First World War, three 6- to 8-foot-wide veins of nearly pure alunite were mined in the southern part of the Sulfur District (Clark, 1918). In 1931, several hundred tons of alunite were mined as a soil additive (Fulton and Smith, 1932). Vandenburg estimated that 454 tons of alunite was shipped to the west coast to be used as fertilizer (Vandenburg, 1938). From 1941 to 1943, cinnabar was mined from small pits in the exposed acid leach zone (Bailey, 1944). Total mercury production during this period is estimated at 1,900 lbs (McLean, 1991).


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5.3Exploration History

In 1966, the Great American Minerals Company began extensive exploration for native sulfur in the area of the Mine. Approximately 200 shallow holes were drilled, and numerous trenches were dug (Friberg, 1980). In 1974, Duval drilled 20 holes on the Hycroft property in search of a Frasch-type sulfur deposit (Wallace, 1980). Duval found no evidence of a sulfur deposit at depth but did report elevated Au and Ag values. Duval drilled two core holes (DC-1 and DC-2) and 18 rotary holes (DR-3 through 20) (Ware, 1989).

In 1977, the Cordex Syndicate mapped and rock chip sampled the Hycroft property, recognizing the potential for a bulk tonnage, low-grade precious metal deposit. In 1978, Homestake became interested in the property, recognizing similarities with the McLaughlin hot springs deposit in California. Homestake completed surface sampling and exploration drilling during 1981-1982, and although successful in defining an oxide Au/Ag mineral deposit, they forfeited the property in 1982. The following mineralization zones shown in Figure 5-1 have been characterized at the Mine.


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Figure 5-1: Predominant Mineralization Zones Identified for the Mine.

Source: Figure prepared by Hycroft Mining, 2022.


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5.4Production History

Information on the production history of the Mine comes from Hycroft’s internal documents. Ore from the Lewis Mine was crushed and stacked on the Lewis leach pads in the north-central part of the Sulfur District. Approximately 259.2 Mtons of ore of a gold grade (AuFA) averaging 0.014 oz/ton was mined from 1983 to 2019 beginning with ore mined from the Lewis Mine followed by ore mined from the Bay, South Central, Boneyard, Gap and Cut-4 pits, and finally the north end of the Brimstone Pit producing over 2.082 Moz of Au.

The Crofoot leach pad (Pads 1 and 2) were constructed in 1987, and Pad 3 in 1992. Ore was placed on Pad 1 from 1988 to 1997, on Pad 2 from 1989 to 1997, and on Pad 3 from 1993 to 1997. Solutions from these pads were treated in the Crofoot Merrill-Crowe plant located on the northeast side of Pad 1.

Production from the Brimstone Pit was placed on the Brimstone pad (Pads 4 and 5) as ROM. Pad 4, constructed just south of the old Lewis pad, was completed in 1996. Loading of Pads 4 and 5 commenced in October 1996 and July 1997, respectively. A 2,800 gallon per minute Merrill-Crowe leach solution plant (the Brimstone Plant) was completed and put into operation in February 1997. The plant treated solutions from Pad 4. Pad 5 solutions were treated in the older Crofoot plant.

In May 2007, the Nevada-based holdings of Vista were spun out into Allied Nevada Gold Corp. The Hycroft Mine was included as part of the transfer of ownership allowing Allied Nevada to explore, expand, and develop the resources at Hycroft.

The Hycroft Mine was reactivated in September 2007 and produced its first doré in December 2008 reaching planned ore production by the end of 2009.

In 2010, the mine began an expansion program that included construction of the North Merrill-Crowe facility, a 21,000 gallon per minute Merrill-Crowe processing plant, and a three-stage crushing facility as well as upgrading their solution pumping capacity. In 2013, Hycroft initiated the construction/expansion of the North leach pad bringing the total leach pad footprint for the Brimstone, Lewis and North leach pads to more than 20 million square ft.

After commissioning the crushing facility in 2014, ROM ore was crushed prior to placement on the heap. Active mining was stopped again at the Mine in June 2015 due to low metal prices, but active leaching of previously mined ore continued through 2018. During this time, Allied Nevada emerged from its financial restructuring to become Hycroft Mining Corporation. In late 2018, Hycroft began construction of new leach pads. In April 2019, active mining began with a focus on transition and sulfide minerals but were set aside for future processing. The crushing facility was also utilized for production in 2019-2020. Only oxide ore was placed on the new leach pads during this time with production of Au and Ag continuing through until 2021.

From September 2007 through July 2019 metal sales have totaled approximately 900,000 oz of Au and 5.0M oz of Ag. Active mining ceased in 2015 and production at the Mine was terminated on November 11, 2021. Table 5-1 lists the annual sales in ounces of Au and Ag produced from the Mine’s heap leach operations over years 2019 through 2021. Annual sales in ounces of Au and Ag produced from the Mine’s heap leach operations over years 2019 through 2021 total approximately 90,000 ounces of Au and 570,000 ounces of Ag.

Table 5-1: Au and Ag Sales from 2019 to 2021


Year	Annual Au Sales (oz)	Annual Ag Sales (oz)
2019	8,373	50,186
2020	24,720	135,293
2021	54,968	385,754
TOTALS	88,061	571,233


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6GEOLOGICAL SETTING, MINERALIZATION, AND DEPOSIT

6.1Geological Setting

The Hycroft deposit is a low-sulfidation, epithermal, hot springs system that contains Au and Ag mineralization. Radiometric dates of adularia (potassium feldspar) indicate that the main phase of Au and Ag mineralization formed four million years ago (Ebert, 1996) when hydrothermal fluids were fed upward along high angle, normal faults. Low-grade Au and Ag mineralization was co-deposited with silica and potassium feldspar throughout porous rock types.

Au and Ag mineralization was followed 0.4 to 2.0 million years ago by an intense event of high sulfidation acid leaching of the mineralized volcanic rocks coincident with a regional water table drop. This allowed steam heated sulfur gases to condense into sulfuric acid and leach the upper portion of the mineralized rocks.

6.1.1Regional Geology

The Hycroft Mine is located on the western flank of the Kamma Mountains in the Basin and Range physiographic province of northwestern Nevada. The Kamma Mountains were formed during Miocene to Quaternary Epoch from the uplift of Jurassic basement rock and emplacement of Tertiary volcanic and sedimentary rocks. The stratigraphy along the western flank of the range is down-dropped to the west, along a series of north to northeast striking normal faults. These faults served as conduits of hydrothermal fluids that deposited the Hycroft mineralization.

The Hycroft property consists of Tertiary to Recent age, fault-controlled, low-sulfidation Au zones that occur over an area measuring approximately three miles in a north–south direction by two miles in an east–west direction. The zones are hosted in volcanic rock eruptive breccias, flows and conglomerates associated with the Tertiary Kamma Volcanics and sand to conglomeratic debris flows associated with the Tertiary Sulphur Group.

Younger rocks at the mine are Tertiary conglomerate, siltstone and fanglomerate of the Sulphur Group (locally termed “Camel Conglomerate”). These rocks are comprised of sediment eroded from the underlying Kamma Volcanics and Jurassic ALS Formation. The Sulphur Group is divided into three main units: a clast-supported coarse conglomerate, a matrix-supported conglomerate, and an underlying tuffaceous lake sediment. This unit outcrops throughout the mine site with increasing thickness to the west.

The older Kamma Group is exposed throughout the Kamma Mountains east of the Central Fault. It underlies the Camel Conglomerate. The volcanic package is comprised of siliceous to intermediate tuffs, coarse grained volcanic clastics, fanglomerates, eruption breccias and massive to flow banded rhyolites.

The Jurassic ALS Formation underlies the Kamma volcanic package. This formation consists of a thin bedded to laminated siltstone, with calcite cementing. ALS is exposed approximately three miles east of the deposit and is encountered only at depth in drilling at Hycroft. A generalized stratigraphic column for the Hycroft deposit area is presented in Figure 6-1. This stratigraphic column illustrates the formations of volcanic origin that host the deposit with notations for lithologies in each formation. The camel conglomerate (Tcm) of the Tertiary Sulfur Group (Tsg) has been broken out as a separate rock, in addition to those shown in Figure 6-1. The sub-group of the Tsg references lakebed sediments that are distinct from the Tcm.


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Figure 6-1: Stratigraphic Column for Hycroft Deposit Area

Source: Figure prepared by SRK, 2019.

Seven major north-northeast trending, west dipping, normal fault zones appear to broadly control the distribution of Au and Ag mineralization as shown in Figure 6-2. From west to east, these fault zones are referred to as the Range, West Splay, Central, Break, Albert, Fire, and East faults. These major structures down-drop stratigraphy and also affect the distribution of alteration and mineralization. A post-mineral basin bounding fault appears to border the Camel Conglomerate and the adjacent Pleistocene Lahontan Lake sediments in the Black Rock Desert. Based on geophysics, this structure is approximately 1 to 2 miles west of the mine site. There are several east–west trending structures that appear to provide post-mineral offset to the deposit. These form a series of horst and grabens within the deposit footprint. Going from north to south, these faults include Cliff, Ramp, Prill, Camel and Hades Faults. Figure 6-2 is a north looking section through the Hycroft Mine showing structures, volcanic rock stratigraphy, and Au/Ag mineralization. There are also several other parallel fault zones that may have a significant impact on the localization of mineralization. The depth of oxide and mixed sulfide/oxide Au and Ag mineralization varies considerably throughout the area. Alteration at the deposit is dominated by acid leaching, silicification, argilization, and propylitization.


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Figure 6-2: Simplified East–West Cross-Sections through the Sulphur District

Source: Figure prepared by Allied Nevada, 2011.

6.1.2Local Geology

The deposit is typically broken into six major zones based on geology, mineralization, and alteration. These include Brimstone, Vortex, Central, Bay, Boneyard, and Camel Hill. The boundaries are typically major faults, namely Break, East, and Ramp.

6.1.2.1Brimstone

The stratigraphy at Brimstone includes up to 100 ft of alluvium, underlain by Camel Conglomerate rocks (0 ft to 400 ft), and Kamma volcanic rocks, as shown in Figure 6-3. ALS has been drilled at depth and is in fault contact (East Fault) with the overlying Kamma Volcanics. The Brimstone ore deposit is hosted primarily by Kamma volcanic rocks in the hanging wall of the East Fault. The volcanic rocks are principally eruption breccias, tuffs, rhyolites, and volcanic rocks proximal to vents, and overlie deformed and metamorphosed shale, sandstone, and siltstone of the ALS group. Kamma Volcanics are strongly altered in the hanging wall of the East Fault, whereas the same units are weakly altered to the east in the footwall of the fault.

At Brimstone, the East Fault is a north-northeast striking, west dipping, normal fault with repeated episodes of movement, including approximately 150 ft to 200 ft of alluvial offset. Where exposed in the Brimstone Pit, the fault clearly shows steep normal movement, with slickensides that plunge 80° to 85°. At depth the fault shallows to 45° to 60° and may merge with the Central and Break Faults. The fault may have originally served as a conduit to hydrothermal fluids. Only minor mineralization is noted footwall to the fault zone.

North of the Brimstone deposit, the east–west trending Ramp and Prill Faults appear to down drop favorable stratigraphy. Condemnation drilling of the leach pad to the north has shown only local zones of weak Au and Ag mineralization. To the south, the Brimstone Zone transitions to the Vortex Zone, with no apparent change in stratigraphy, but changes to alteration zonation.

Host rocks were highly altered by at least four phases of alteration. The relatively porous conglomerate and breccias were preferentially acid leached by late stage steaming hydrothermal acid vapors. Acid leach alteration extends to depths of 700 ft in some areas of the Brimstone deposit as seen in Figure 6-3, indicating that the water table was present below the base of the acid leached zone. A siliceous layer (basal acid leach), up to tens of feet thick, occurs at the base of the acid


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leached material. Underlying the acid leaching is a layer of hydrothermal clay alteration, followed by silica potassium feldspar alteration. Pervasive silicification, veining and hydrothermal brecciation are generally found in the rhyolites and breccias.

Zones of silicification of limited thickness, oriented parallel to the East Fault, are present in the footwall zone. Alteration extends for 50 ft to 70 ft footwall to the fault, with pervasive silicification and quartz veining dominant.

Figure 6-3: Brimstone Generalized Geology Cross-Section

Source: Figure prepared by Allied Nevada, 2011.

Au and Ag are spatially associated with fracture and breccia-controlled chalcedony sulfide mineralization. A subsequent acid alteration event produced the current distribution of oxidized and transition sulfide/oxide ore. The lower acid leach material hosts Au and Ag mineralization, as does the underlying silicified and veined volcanics.

Drilling has shown that mineralization extends to a depth of over 1,200 ft in the Brimstone Zone. Mineralization thickness (true width) is 200–1,100 ft thick and remains open to the west toward the Break Fault and transitions into Vortex to the south.

6.1.2.2Vortex

The stratigraphy in the Vortex Zone is correlative with those at the Brimstone Zone immediately to the north. Camel Conglomerate is underlain by tuffs, volcanic clastics, fanglomerates, and rhyolites of the Kamma Volcanics. The ALS is present, footwall to the East Fault, and appears to be in stratigraphic contact with the Kamma Volcanics, as seen in Figure 6-4.


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The upper elevation at Vortex is hydrothermally clay (kaolinite) altered. Acid leaching is less prominent in Brimstone and is focused primarily along the East Fault. Strong silicification to depths greater than 1,500 ft is due to veining and phreatic hydrothermal brecciation. At least four mineralizing events are present as evidenced by crosscutting vein and breccia relationships. The hydrothermal venting may have contributed to the eruption breccias overlying the Brimstone Zone. Propylitic and/or clay alteration extends outboard of the silicification.

The mineralization at Vortex is of both vein and disseminated type, with brecciated and altered rhyolite rocks and volcanic clastics acting as favorable hosts. In addition to Au mineralization, high-grade Ag has been encountered at Vortex; with values ranging from 10 to 647 oz/ton. The predominant Ag minerals are pyrargyrite, naumannite and miargyrite, occurring both in veins, disseminated and coarse grains along fractures.

Oxide mineralization is present at a depth of approximately 500 ft below surface, with sulfide mineralization extending to 2,500 ft below surface. Mineralization thickness (true width) is 1,000 to 1,800 ft thick. Banded quartz veins with both high-grade Ag and Au have been noted in core. Drilling to date indicates that the high-grade zones are both high angle banded quartz veins and a more extensive flat lying, massive quartz zone containing visible pyrargyrite and miargyrite.

Figure 6-4: Vortex to Camel Hill Generalized Section

Source: Figure prepared by Allied Nevada, 2011.

6.1.2.3Bay and Boneyard

Mineralization in the Bay and Boneyard zones is hosted by gentle, west dipping Camel Conglomerate. Both clast-supported and matrix-supported conglomerate rocks host mineralization. The basal rock type is tuffaceous lake sediments, composed of fine-grained clay with minor layers of gravel and conglomerate extending to a depth greater than 1,100 ft as shown in Figure 6-5. Mineralization is primarily bedding controlled, with the Range and Central Faults as the main feeders. The Break Fault may also have zoning controls but is poorly drilled in this zone. Mineralized siliceous hot spring sinters have been historically mined indicating that this deposit represents the upper-most levels of a hot spring hydrothermal system.


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The predominant alteration type at Bay is silicification. Acid leach alteration in the area is relatively minor and occurs along high angle structures. Clay alteration of the underlying lacustrine sediments is also noted in limited drillholes and is illite smectite dominated. Strong oxidation is present in the upper portion of the silicified zone.

Au and Ag mineralization is associated with flat lying Camel Conglomerate, above the lacustrine lake sediments. Mineralization thickness (true width) is 20–250 ft thick at Bay and 50–300 ft thick at Boneyard. This zone transitions into the upper zone of mineralization at Central. Bay and Boneyard remain open to the north and east.

Figure 6-5: Bay Geologic Cross-Section

Source: Figure prepared by Allied Nevada, 2011.

6.1.2.4Central

The Central Zone geology is similar in nature to that of Bay, with mineralization and alteration fed by high angle faults and fractures, with dominant lateral fluid flow through the porous conglomerate rocks of the Sulphur Group as seen in Figure 6-5. Camel Conglomerate units are underlain by lacustrine sediments. However, the lacustrine units thin dramatically to the south, with less than 50 ft of the material noted south of Cut-4.

The Central Zone is bounded to the east by the Central and Break Faults. Fault movement is unknown, but extends at least 2,000 ft, with recent reactivation in the quaternary (50–150 ft), as demonstrated by offset in the alluvium. The Range Fault to the west may provide an additional boundary, although drill data is limited at this time. Alteration along the Central Zone is similar to that of Bay. Acid leach alteration is stronger and more widespread than at Bay and is extensive in the southern portion of the pit. The acid leaching overlies silicified conglomerate rocks, except along the immediate trace of the Central Fault where silicification dominates as the alteration type. Oxidation extends downward approximately 400 ft. Underlying the silicification and acid leaching are illite-smectite clay altered and clay dominant lacustrine sediments. Hot spring sinter deposits have not been observed.


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Au and Ag mineralization is associated with favorable stratigraphic horizons in the Camel conglomerate, with an upper and lower zone noted in drilling, separated by a north–south striking, east dipping clay layer. Mineralization remains open to the west, past the Range Fault, and at depth (>1,400 ft). Mineralization thickness (true width) in the upper zone is 50 300 ft thick, while the lower zone ranges from 300–1,200 ft thick and remains open at depth. The zone mineralization is contiguous to the Vortex and Brimstone Zones to the east, and the Camel Hill/Cut-5 zones to the south.

6.1.2.5Camel Hill and Cut 5 Zones

Camel Conglomerate is the dominant lithology at Camel. The conglomerates appear to extend to depth in this zone, with only thin lake sediments drilled to date. The lack of lake sediments can be attributed to either the Camel Fault or facies changes along a shoreline. The Camel Fault is an east–west trending fault, with down-drop to the south, which is presently poorly defined by drilling.

Alteration south of the Central Pit and in the Camel Zone is predominantly comprised of silicification and clay alteration. Hydrothermal clays, overlying silicified conglomerate rocks, and basal illite-smectite clay altered rocks are present. Acid leaching in the area is relatively minor, especially with respect to the intensity and amount in the Central and Cut-4 Zones area immediately to the northeast.

Mineralization in the Camel/Cut-5 Zones is hosted by conglomerate rocks and occurs as both disseminated Au and Ag associated with pyrite and marcasite, and higher-grade veins, including Ag bearing pyrargyrite veins. Mineralization thickness (true width) is 200–1,100 ft thick, extends to depths greater than 1,400 ft, and remains open at depth. Oxidation extends to depths greater than 200 ft and an area of intense oxidized mordenite alteration is present between the Cut-5 and Camel Zones. Mineralization remains open to the south, west and at depth. To the north, Camel mineralization is contiguous with the lower zone of the Central Zone, while Cut-5 is contiguous with the upper zone. Mineralization is also open to the west of Camel and to the south towards Hades Fault.

6.2Alteration and Mineralization

Detailed geologic work by previous owners at Hycroft identified a number of hydrothermal alteration events. However, for resource estimation purposes, there are four alteration types that have been interpreted and assigned to the block model.

•Acid Leach – Associated with the upper portion of the epithermal vent. Native Sulfur is common in this area and the original protolith has been obliterated with a white clay alteration.

•Propylitic – Propylitic altered material is generally found in the volcanic rocks of the Kamma Mountains. Although it is occasional interpreted within the mineralized zone of the deposit.

•Argillic – A pervasive alteration of both the Camel Conglomerates and the Kamma Volcanics. Where clay minerals have replaced the original potassium feldspars and other minerals.

•Silicic – Silica flooding which is associated with the mineralization processes at Hycroft.

Acid leach will not be sent to the process facility or to the leach pad due to the high levels of sulfides and native sulfur. It has been estimated but the minor remaining tonnage is not included in the mineral resource.

Propylitic is generally barren or nearly so. It has been lumped with the argillic alteration units for grade estimation and assignment.

Silicic alteration is generally better grade than the surrounding argillic and is mechanically more robust.

Oxidation has occurred across the deposit to variable depth depending on the structural preparation and available acidic ground water. The oxidized material has been the historical ore for heap leaching at Hycroft. This study includes ROM leaching of low-grade mineralization and flotation of mineralization with sufficient pyrite and other sulfides to generate Au and Ag rich concentrate.

Figure 6-6 is a generalized east–west section illustrating the alteration at Hycroft.


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Figure 6-6: Generalized Hycroft Epithermal Diagram

Source: Figure prepared by Allied Nevada, 2011.

6.3Deposit Types

The Hycroft deposit is a large, epithermal, low-sulfidation hot springs deposit (Figure 6-6). Au and Ag mineralization are noted as both disseminated and vein controlled.


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7EXPLORATION

7.1Drilling

The Hycroft exploration model includes data from 1981 to 2018 and includes 5,501 holes, representing 2,482,722 ft of drilling (Figure 7-1). There have been 5,576 drillholes reported completed in the Hycroft Project Area; some are water wells or are outside the resource model domain and were not applied to estimation. The drillhole collar locations are shown in Figure 7-1. At this time, there are 5323 drillholes in the resource model area of which 134 have been drilled to define stockpiles or the Crofoot leach pad. Section 8 provides a more detailed breakdown of the amount of drilling and assaying for use in resource modeling.

Exploration drilling was started in 1974 by Duval Corporation, which was evaluating the property for a Frasch-type sulfur deposit and the copper potential. Although native sulfur appeared to be limited to the acid leach zone, Au and Ag mineralization was discovered at depth, with the deepest hole completed to 2,000 ft. Duval concluded that the property did not have large scale sulfur potential. Twenty drillholes (9,726 ft) were completed on the project.

From 1981 to 1982, Homestake, using their McLaughlin deposit as a model, completed 96 RC drillholes totaling 16,537 ft, primarily in the Bay and Boneyard areas. Shallow oxide Au mineralization was discovered, but Homestake declined the opportunity. Crofoot and American Slag then proceeded to acquire the property rights and initiated small-scale oxide heap leach mining at Central and Bay in 1983. Homestake also completed 8 core holes during this timeframe, but collar location data has not been located.

Hycroft gained control of the district in 1985 and drilled 3,212 exploration holes, totaling 965,552 ft, between 1985 and 1999. The bulk of this drilling was shallow and focused on oxide Au mineralization at Central, Bay and Brimstone.

In 2005, Canyon Resources completed 33 drillholes totaling 13,275 ft of RC drilling. These were completed primarily in the Brimstone Pit area.

Hycroft commenced systematic exploration and resource development drilling starting in 2006. Drilling has been focused on oxide resource delineation, sulfide resource definition, sulfide exploration, condemnation drilling for facilities, Ag data and both geotechnical and metallurgical core samples. Between late-2006 and August 31, 2016, Hycroft has completed 1,970 exploration holes, totaling approximately 1.45 M ft.

A combination of rotary, RC and core drilling techniques has been utilized to verify the nature and extent of mineralization. The majority of samples have been collected using RC drilling methods on 5-foot sample intervals. RC drilling utilizes 4.5- to 5.5-inch tooling. Deeper drilling is conducted with diamond drilling, using PQ, HQ and NQ tooling. This practice continued through 2013. Since 2013, a RC drilling program was completed in 2014, and a metallurgical core program with the six drillholes was completed in 2017. The metallurgical drillholes were not included in the database for mineral resource estimation and are not shown on the drill hole location map. Various protocols applied to drilling by Hycroft are consistent with industry standards and the resulting data is of good quality for use in the Hycroft model. Shallow drillholes to sample heap material were completed with sonic coring. The 2018 sonic drilling program was limited to 56 vertical holes in sulfide stockpiles and did not include in-situ alluvium or bedrock material. While these were not used for interpolation of in-situ rock, they were applied to estimate grades in fill material.


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Figure 7-1: Drillhole Collar Locations

Source: Figure prepared by IMC, 2022.


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7.2Additional Exploration

In addition to drilling activity, Hycroft has also conducted geophysical surveys, soil and rock chip sampling programs, field mapping, historical data compilation, and regional reconnaissance at the Mine site. These efforts are designed to improve the understanding of the known mineralization, as well as provide data for further exploration of the greater property position.

A soil sampling grid was conducted over the Vortex and Brimstone areas historically (1,797 samples) and was extended approximately 5,200 ft north and 29,600 ft south of the mine in 2011–2012 (1,834 samples). The soil sampling program was conducted primarily along the East Fault exposure, which is a primary ore-controlling feature at Vortex and Brimstone. Results, using Au, Ag, arsenic, and antimony, indicate potential exploration targets to the south of the Vortex area. At present these have been identified as the Wild Rose, Chance, Rabbit, Chalcedony, and Oscar target areas. Au values range from 0 to 0.027 oz/ton, while Ag values range from 0 to 3.7 oz/ton. Soil samples are taken on an evenly spaced grid, and screened for coarse material and wind-blown material, resulting in a fraction between 2 mm and 180 um being prepped for analysis. These samples are considered representative of local soil geochemistry and are used to guide the regional exploration effort.

Rock chip sampling has been conducted both historically in the active mine area, and on a regional basis (2007–present). A database of 2,416 samples has been compiled, covering the greater land position. Using Au, Ag, arsenic, and other elements, exploration targets have been developed both north and south of the current mine. These include Wild Rose, Chance, Oscar, Rabbit, Floka, and Cliffs. Au values range from 0 to 0.372 oz/ton, while Ag values range from 0 to 71.8 oz/ton. Rock chip samples have been taken on most outcrops, with a focus on alteration and potential mineralization. These samples are used as a guide to exploration and are point samples only.

The land position has been surveyed with both gravity and induced polarity (IP) geophysical techniques by Hycroft. The current ground-based gravity survey covers approximately 130 square miles, centered on the mine site. Gravity indicates several structural features and density changes that offer potential exploration targets. These targets include Floka, Blowout, and Oscar. Gravity has also defined the basin edge to the west, approximately 4 miles west of the Brimstone Pit.

Ground IP surveys were run over the mine site and Vortex in 2007 and extended outward in 2011 to cover approximately 24 square miles. The survey results focus on chargeability anomalies, that potentially identify sulfide material (> approximately 1.5%) at depth, and resistivity anomalies, that potentially identify silicification at depth. Results have identified additional exploration targets at Floka, Cliffs, Blowout, Wild Rose, and Chance.

Field mapping was historically and is currently carried out in all active mine areas. Mapping focuses on structure, bedding, joints, lithology, and alteration. The near mine data is incorporated into the three-dimensional geology model, while the regional work is focused on defining exploration targets for future drilling. A regional geology map covering the land position was compiled in 2012 (Figure 6-3). Regional exploration data from Homestake, LAC Minerals, USX, HRDI, and others has been compiled from both in-house and public data sources. Approximately 250 drillholes, various soil and rock chip locations and results, and various field maps have been identified at present.


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8SAMPLE PREPARATION, ANALYSES, AND SECURITY

This section describes the sample collection, preparation, analysis and security that has been used by Hycroft or their predecessors. Drilling and sampling at the Mine have been ongoing from 1982 through 2020. Hycroft provided IMC with the database which contained assay information for drilling from 1982 through 2018. IMC is the qualified organization for the section.

Most of the current staff at Hycroft have been at site less than 3 years. As a result, much of the information that is reported here regarding historical sample preparation, analysis, and security was previously reported in a Technical Report Summary prepared by M3 and SRK in July of 2019 titled “Technical Report Summary, Heap Leaching Feasibility Study, Winnemucca, Nevada, USA”, July 31, 2019. IMC has confirmed that information as much as possible with the data provided.

8.1Sample Preparation

Sample preparation procedure prior to 1999 was not documented. Starting in 2005, preparation procedures were well documented standard methods. The comparison of the pre-2005 data with post-2005 drilling will be presented in Section 9 to provide some confidence in the application of the pre-2005 data.

Post-2005 sample collection consisted of both diamond core and RC drilling. Core samples are currently split at the mine site, tagged, and the split core is sent to commercial laboratories for further preparation. Reverse circulation samples are currently collected at the rig with a rotary splitter. Bags of RC cutting splits are tagged and sent to commercial laboratories for further preparation and assaying.

Once at the commercial labs, the samples are crushed to 10 mesh and a 2.2 lb (1 kg) split is taken and pulverized to 85% passing 200 mesh prior to assay analysis.

8.2Assay Methods

Prior to 1992, most samples were sent to Barringer Laboratories, Inc., in Golden, Colorado. Fire assays were routinely performed on cyanide soluble assays for selected intervals. From 1992 to 1999, samples were processed at the Hycroft laboratory at the mine site.

The Hycroft laboratory assays consisted of fire Au followed by cyanide soluble Au and cyanide soluble Ag on all intervals. Hycroft cyanide soluble assay methods are reported to have been non-standard and were developed to provide a prediction of recoverable Au and Ag from heap leaching.

There are no samples in the database for the time period from 2000 through 2004. Starting in 2005, all samples were sent out to commercial labs for analysis. During 2012, there were 10 drillholes that were an exception to this rule that were assayed by the Hycroft lab. Those holes have reportedly been compared with assays from commercial labs and are still maintained in the database.

The external labs that have been used by Hycroft are all in the Reno/Sparks, Nevada area and are listed below with their accreditations:

ALS Minerals ISO9001:2000 and ISO17025

American Assay Laboratories ISO/IEC17025, PTP-MAL Canada

Inspectorate ISO9001:2008

McClelland ISO/IEC17025

All intervals were assayed using conventional fire assay with Atomic Absorption (AA) or gravimetric finish for Au. Fire Ag assays were not regularly completed by previous project operators. After 2013, aqua regia digestion was used for total Ag assays and replaced the previous gravimetric treatment of Ag. The lower detection limit on the aqua regia method was the reason for the change.

The fire assay method for Au with an AA finish was the primary assay method at all of the labs. Cyanide soluble methods were alternatively hot or cold cyanide depending on the lab.


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As noted previously, cyanide Ag was much more consistently assayed than total Ag. During the period from 2005 until 2013 roughly 63% of the drill intervals with Au assays were analyzed for total Ag. Starting in 2014, total Ag was consistently assayed along with fire Au.

Cyanide soluble assays for Au and Ag were highly prevalent in the pre-2000 drilling. As drilling began to target the deeper sulfide mineralization after 2005, the cyanide soluble assays were selectively run on the upper, oxidized portion of the deposit and not applied to the deeper sulfide mineralization.

During 2007 and 2008, Hycroft also applied 35 element Inductively Coupled Plasma (ICP) analysis to roughly 90% of the assay intervals. That data results in 53,624 sample intervals that can be used to track trace elements.

During 2011, 127 drillholes were selected for ICP and Laboratory Equipment Corporation (LECO) analysis at American Assay. These holes were generally on 500 x 200-foot centers across the estimated sulfide pit target at the time. Most were assayed on 25-foot intervals from top to bottom for total sulfur, sulfide sulfur and carbon. During 2014, additional sample intervals were selected from the 2012 to 2014 drilling for LECO and ICP.

The sulfide sulfur results from this work have been used to assign sulfide sulfur values to the block model for process metallurgical input. It should be noted that the sulfide sulfur procedures also report elemental sulfur along with the sulfide component.

Assay submittals have included blanks and standards since at least 2007. Check assays and duplicate assays were submitted in 2012 and 2014. The results of the analysis of those samples will be reported in Section 9.

8.3Sample Security

Samples were delivered to the analytical laboratories in numbered bags along with transmittal sheets that list the sample numbers, the total sample count, and codes for sample type (RC or Core). The lab confirmed the receipt of shipment against the transmittal sheets to account for all samples issued.

It is reported that no officers, directors, or associates of Hycroft or their predecessors were operationally involved in the sample collection, preparation, or assay transmittal.

8.4Analytical Results

Following analysis, results are posted to a digital laboratory database for which Hycroft has secure permission privileges. Managers download the data where the sample results are cross-referenced to sample numbers. Each drillhole carries a unique self-identifying sample number, simplifying the cross-referencing. The completed digital file for each drillhole is emailed to Hycroft by the lab and a follow-up, hard copy certificate is mailed to company offices.

Data is checked by geologists visually and loaded into the secure acQuire database. The acQuire database is further checked using electronic methods and then calculated into ounce per ton values and loaded to the modeling database for display and further visual QA/QC checking.


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9DATA VERIFICATION

This section will address the QA/QC results on drilling completed since 2005 in order to establish the validity of the post-2005 drilling. The post-2005 drilling will be compared to the pre-2000 drilling on a nearest neighbor basis to confirm the applicability of the old drilling data to resource estimation. The qualified organization for this section is IMC.

Hycroft has a history where gold fire assays collected prior to 2000 were factored upward in order to better correlate with blast hole assay results pre-2000. That factor process has been removed from the database for application to this mineral resource. The basis for the removal will be discussed later in the text.

The pre-2000 drilling data at Hycroft has no historical QA/QC information to support it. The post-2005 drilling data (no drilling in 2000 to 2004) has QA/QC information that is sufficient but not best practice. With the corrections noted in this section, IMC has accepted the database for determination of mineral resourcess. Hycroft has begun to implement best practices for data collection and QA/QC and will continue to update those procedures in the future.

9.1QA/QC Post 2005

The following QA/QC data is available for the drilling data collected after 2005:

•Standards and Blanks.

•Check Assays from 2011 through 2013.

That information will be analyzed to understand the relative reliability of the post-2005 drilling.

9.1.1Standards

Blind standards are inserted into the assay samples for analysis at the assay lab. The lab obviously knows the sample is a standard, but they do not know which standard.

The standards database provided to IMC did not include dates of insertion. It is presumed that the insertion of standards started in 2005 with the modern drilling program. However, the earliest example of standard acquisition that IMC could find was mid-2007. There are indications of sample insertion though the 2013-time frame.

In most exploration environments, standards results are reviewed as they arrive from the lab to confirm that the measured result is within the error tolerance reported for the standard. IMC takes a different approach and compares the accepted value of the standard against the multiple assays of the standard on an XY plot in an effort to identify any potential bias in the assay process.

Figure 9-1 illustrates the results of the standards submissions for gold.

The comparison of the accepted value of the standard and the tested standards results does not indicate a consistent bias. The points that are scattered off access likely reflect swapped samples meaning that the wrong standard was recorded or submitted to the lab compared to the tabular results. There are roughly 22 apparent sample swaps out of a total of 7,154 tested standards or about 0.3% of the original samples.

Figure 9-2 summarizes the results of the total Ag standards submissions. There is substantially more variation in the Ag standards results as one would expect in this grade range. In addition, most of the original assays are gravimetric finish which have a detection limit of 5 ppm or 0.15 oz/ton. Three are only five standards results below 0.15 oz/ton out of 6,498 Ag standards analyzed. With some standards values as low as 0.20 oz/ton it would not be out of line to see an indication of subtle bias if the lowest value that can be reported is 0.15 oz/ton.


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Figure 9-1: Results of Submitted Gold Standards

Source: Figure prepared by IMC, 2021.


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Figure 9-2: Results of Submitted Silver Standards

Source: Figure prepared by IMC, 2021.

9.1.2Blanks

Blank samples are inserted periodically to confirm that metal is not carried over from one sample to the subsequent sample in the sample stream. Figure 9-3 summarizes the results of the blank submissions for gold from 2008 to 2014. The figure indicates that the majority of samples reported back as trace or small values.

However occasional samples have been reported near or above heap leach feed grade. Of the 2,260 standards in Figure 9-3, 5.9% reported higher than 0.005 oz/ton and 5.6% reported higher than 0.010 oz/ton. Although small percentages, there is room for improvement.


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One expects that some of the samples were not blanks but were misaligned standards. The average of the values that are above 0.005 oz/ton is about 0.019 oz/ton, which is quite close to the standard value of the Cove 2 standard.

Figure 9-3: Results of Blank Submissions

Source: Figure prepared by IMC, 2021.

9.1.3Check Assays

Assay pulps were submitted to a second lab as check assays during 2011–2012. The primary lab was ALS and the check lab was AAL. The results are summarized in Figure 9-4 through Figure 9-5 as XY plots.

The variability in the results is more than one would expect from pulp submissions, but there does not appear to be an observable bias in the laboratory comparisons. The line on the graphs illustrates a 1:1 relationship as a comparison.


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Figure 9-4: Check Assay Results, Fire Assay Gold 2011 - 2012

Source: Figure prepared by IMC, 2021.

Figure 9-5: Check Assay Results, Fire Assay Silver 2011 – 2011

Source: Figure prepared by IMC, 2021.


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9.1.4Certificates

IMC requested copies of the certificates of assay from Hycroft in order to spot check the database provided against the original laboratory reports. Those certificates were provided in two iterations. The first group of 20 certificates was received in late September 2021. The second group was received on 11 December 2021 as this report was being prepared. The second set of certificates received a cursory review as time was not available for a more complete review.

Of the first 20 certificates, there were 11 assay intervals out of 4,417 checked intervals where the database fire gold data did not match the certificate. That error rate of 0.25% is acceptable. Drillhole H12D-4320 had certificates of assay for the LECO assays. No errors were found in the spot check of LECO data within that hole.

The later batch of certificates received in December reflected 11 holes drill prior to 2000, and 27 holes after that date. The certificates from the more recent assays include information from ICP analysis and LECO for some holes in addition to the gold and silver assays.

The 11 holes prior to 2000 ranged in dates from 1990 to 1996. Eight of those holes were gold fire assay certificates and three were fire Ag assays. A scan of the eight holes with fire gold assays found no errors when compared to the database.

This observation is inconsistent with previous resource reports and the statistical analysis to follow which both indicate that the gold fire data prior to 2000 were all factored upward by a multiplier of 1.19. There are 3,313 drillholes in the database that were drilled prior to 2000. Of those, the eight certificates that were checked did not indicate that the database has been factored.

This issue warrants more investigation in the future. For this study, IMC has removed the reported 1.19 factor by multiplying all gold assays prior to 2000 by 0.84 based on the statistical analysis and previous resource reports. This approach is the conservative choice, even though it ignores the results from the eight certificates of assay.

9.1.5Old vs. New Drilling

As noted above, previous Technical Reports regarding the Hycroft mineral resources had reported that all gold assays prior to 2000 were factored upward. Those in acid leach alteration were factored upward by 1.32 and all others upward by 1.19 (Hycroft Project Mill Expansion Feasibility Study Technical Report, October 31, 2016 and Technical Report, Allied Nevada Gold Corp, Hycroft Mine, October 2011).

Discussions with Hycroft geologists at site indicate that they believe the gold database prior to 2000 to have been up-factored. The original source of the factor was work by MRDI in May of 2000 comparing the exploration RC drilling to the blast hole assays for production. Their conclusion was that the RC drilling was low biased and as a result the grades from the pre-2000 drilling should be factored upward. It is curious that the potential for high bias of blast holes was not considered. Common blast hole sampling methods are often high biased for gold due to concentration of gold in fines and preferential sampling of fines from blast holes.

IMC embarked on a comparison of pre-2000 drilling (Old) versus the post-2000 drilling (New). A nearest neighbor approach was used where the 40 ft drill hole composites were sorted to find Old drill composites that were close to New drill composites. The pairs of Old and New composites were sorted into separation distances ranging from 10 to 50 ft. For reference, the size of one model block was 40 x 40 x 40 ft. Table 9-1 below summarizes the results for composites within the Argillic, Silicic, and Propylitic alteration units.

Table 9-1: Nearest Neighbor Sample Comparison of Pre-2000 Gold Composites versus Post-2000 Gold Composites


Maximum Separation Distance ft	Number of Sample Pairs	Pre 2000 Mean oz/ton	Post 2000 Mean Oz/ton	Ratio of the Means	T-Statistic
10	48	0.017	0.015	1.13	0.83
20	220	0.014	0.011	1.27	2.32
30	493	0.013	0.011	1.18	3.27
40	764	0.013	0.011	1.18	4.03
50	1,107	0.012	0.010	1.20	4.66

T-Statistic is the Smith-Satterthwaite T for Large Populations


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The results of Table 9-1 indicate that the Old gold assays are between 1.18 and 1.20 times higher than the New gold assays. The results are remarkably close to the reported 1.19 factor that has reported as applied to the Old (Pre-2000) gold assays. The T-Statistic reported on the right side of the table is comfortably above the value of 2.0 for the sample separation distances of 20 ft or greater. If the T-Statistic is greater than 2.0 one should reject that the two data sets are similar. Both RC and DDH drilling have been used in the above analysis.

As a result of the above analysis, previous Technical Reports, and the opinions of site staff, the upgrade factor was removed prior to estimation of mineral resources by refactoring all pre-2000 Au assays by 0.84 (1/1.19).

9.1.6DDH vs RC

The drillhole database at Hycroft is predominately based on RC drilling with some diamond core drilling (DDH). Prior to 2000, the database does not provide a record regarding the type of drilling applied, although it was reported to be largely RC.

Since 2000, the database records whether the drilling was RC, DDH, or sonic. The sonic drilling was applied in stockpiles which are a minor component of the remaining mineral resource.

The RC data was compared to diamond using the nearest neighbor method that was described in the previous sub-section. Table 9-2 summarizes the results of that comparison.

Table 9-2: Nearest Neighbor Sample Comparison of RC Gold Composites versus DDH Gold Composites


Maximum Separation Distance ft	Number of Sample Pairs	RC Mean oz/ton	DDH Mean Oz/ton	Ratio of the Means	T-Statistic
10	87	0.010	0.012	0.83	1.03
20	192	0.010	0.011	0.91	1.33
30	297	0.010	0.011	0.91	1.56
40	392	0.010	0.012	0.83	2.43
50	504	0.010	0.011	0.91	2.69

T-Statistics is the Smith-Satterthwaite T for Large Populations

The results indicate that the RC may be marginally low biased compared to DDH, but the results are sufficiently close so that both data sets have been accepted for mineral resource estimation.

9.1.7Downhole Surveys

During the last half of 2021, Hycroft completed several drillholes that are primarily intended for metallurgical samples. In the process, a review of the downhole surveys found that the drillhole bearings were properly recorded relative to true north. However, the Hycroft resource model and database has been rotated 16 degrees to the right of true north.

As a result, the downhole surveys must also be rotated 16 degrees in order to align with the mine site and model grid. Hycroft personnel initiated a thorough check of historical downhole surveys versus that stored in the database. As a result, the downhole surveys were corrected on 891 drillholes (16.9% of the database) prior to calculation of composites or use in the development of mineral resources. The original survey was reduced by 16 degrees in order to align with the mine site coordinate system.


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10MINERAL PROCESSING AND METALLURGICAL TESTING

Hycroft has been operating the Mine as an open pit mine and run-of-mine (ROM) heap leach facility for their oxide ores to produce gold and silver since 2008. Prior to that, Vista Gold operated the Mine in a similar manner. The cumulative performance statistics and metallurgical test data gathered for the direct cyanidation of high-grade ROM oxide ore via heap leach are extensive and not the focus of this report. The following subsections focus on testwork done by Hycroft on extraction of Au and Ag from their refractory sulfide mineralization.

The metallurgical test programs conducted on the Hycroft sulfide mineral deposits over the years has consisted of comminution, flotation, concentrate oxidation, and cyanide leaching tests on mineralized materials, flotation tailings, and oxidized sulfide concentrate samples. The samples were mostly derived from drill cores. The bulk of the flotation tests were conducted at G&T and SGS, both in Canada, and by Hazen in Colorado. Oxidation testing was primarily conducted by Hazen, SGS and KCA.

In general, core samples for metallurgical testing were selected to represent the mineralized materials, taking samples from five mineralization domains, as they were classified at the time. The main sources were Central, Brimstone and Vortex domains.

10.1Mineralized Materials and Sampling

Hycroft mineralized materials are classified as “oxide,” “transition,” or “sulfide,” depending on the solubility of its gold content in cyanide solution (refractoriness). Materials having cyanide soluble gold contents of 70% or higher are classified as oxide. Those with cyanide soluble gold contents below 30% are considered sulfide. The remainder, with cyanide soluble contents between 30 to 70% are considered transition. The classification has been shown to have no strong correlation with sulfide sulfur content.

10.1.1Hycroft Mineralization Domains

The Hycroft mineral deposit consists of five process domains, namely Bay, Boneyard, Brimstone, Central, and Vortex.

Table 10-1 is a summary of the data for average total sulfur, sulfide sulfur, and the ratio of sulfide sulfur to total sulfur from 95 oxide, 158 transition and 417 sulfide samples originating from the Brimstone, Central, and Vortex domains. It shows that the classification of the ores as oxide, transition, or sulfide is essentially a measure of refractoriness and has little correlation with the sulfide-sulfur content of the minerals. Sulfide-sulfur: total sulfur ratio averages slightly over 80% for the entire dataset. This indicates that degree of oxidation of sulfur is the same among oxides, sulfides, and transition.


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Table 10-1: Average Sulfur Contents of Oxide, Transition and Sulfide Mineralized Materials


Total S (ST), %	Oxide	Trans	Sulfide
Brimstone	2.55	2.41	2.25
Central	2.94	2.82	2.48
Vortex	2.47	2.66	2.33
Unclassified	4.28	2.92	2.61
All	3.00	2.74	2.43

Sulfide S (S=), %	Oxide	Trans	Sulfide
Brimstone	2.19	2.06	1.87
Central	2.36	2.26	1.80
Vortex	2.09	2.23	1.91
Unclassified	3.29	2.23	2.09
All	2.45	2.23	1.93

S=: ST Ratio	Oxide	Trans	Sulfide
Brimstone	0.839	0.839	0.820
Central	0.810	0.806	0.797
Vortex	0.880	0.827	0.833
Unclassified	0.840	0.823	0.843
All	0.849	0.819	0.824

10.1.2Samples for Metallurgical Testing

Table 10-2 below lists the number of samples selected to span the three main domains and distributed in the mineral deposit.

Individual core samples selected for testing may be found in copies of the test reports analyzed for this study.

Table 10-2: Summary of Test Samples


Tests	Number of Samples per Domain
	Central	Brimstone	Vortex	Composite*
Crushing (CWi)	1	1	5	7
Axb (Drop Wt & SMC)	13	6	9	32
Bond BWi	24	6	16	58
Bond RWi	2	1	0	5
Bond Abrasion	3	1	5	12
Flotation	11	13	24	48

10.2Comminution Tests

The Hycroft mineral deposit has been thoroughly characterized for its comminution properties in the previous studies. The comminution tests were conducted at laboratories of SGS, G&T, Hazen, and Phillips. These include crushing and grinding work indices, JKSimMet parameters A, b and ta, and abrasion indices.

A summary of the 80th percentile comminution test results is in Table 10-3 below. For the Axb parameter, because hardness competence increases as Axb decreases, the 80th percentile in hardness competence corresponds to the 20th percentile of Axb.


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Table 10-3: Grindability Test Summary


Parameter	Unit	Value
CWi	kWh/ton	18.6
RWi	kWh/ton	21.2
BWi	kWh/ton	20.1
Axb	unitless	34.2
SPI (min)	min	102.4
Ai (g)	g	0.623

10.3Flotation

10.3.1Review of Flotation Testwork

Refractory gold, in Hycroft’s sulfide mineralized materials, is believed to be associated in iron sulfides, primarily pyrite and marcasite. The goals of these tests are to determine the floatability of the sulfides, and the recovery of Au and Ag in the sulfide concentrate. The ability to recover Au and Ag in the sulfide concentrate reduces the volume of material to be treated.

Initial flotation testwork was performed by SGS in March of 2009 and continued at several laboratories until April of 2014. During this time frame, the testing program began with bench-scale tests and moved into pilot plant scale flotation tests at G&T and Hazen.

10.3.1.1SGS Minerals Services (Lakefield) – March 2009

Six drums containing samples representing the Hycroft Project were sent to SGS Minerals Services (Lakefield) on September 5, 2008.

The initial flotation test series consisted of three bench-scale rougher kinetics tests to evaluate the effect of primary grind size on flotation response. A standard set of bulk sulfide collectors consisting of xanthate (PAX) and dithiophosphate (Cytec AF 208) was applied along with Dowfroth 250 frother. An additional five bench-scale tests were run to investigate other reagent schemes and grind sizes.

Flotation testwork was conducted on the Master Composite sample. The flotation investigation consisted of the following:

•Two-stage cleaner flotation applying the flowsheet developed in phase 1 testing (program 12012-001),

•Cyanide leaching of the 2nd cleaner flotation concentrate, and

•Cyanide leaching of the recombined rougher and 1st cleaner scavenger tailing.

SGS stated “In terms of sulfide flotation, it appears that beyond about 10% mass pull, recoveries were on the same grade vs. recovery curve regardless of grind fineness.

10.3.1.2SGS Minerals Services (Lakefield) – Nov 2010

Batch tests were completed on 33 sulfide zone composites representing the Vortex (18), Cut 5 (4), Bay Area (10), and Bone Yard (1) deposits of the Hycroft mine sulfide resource. Several rock types were represented in the composites. The testwork examined the metallurgical variability of the samples in response to the flotation (and cyanidation) flowsheet previously developed for the Master Composite in program 12012-001.

Metallurgical variability testing consisted of rougher flotation followed by concentrate regrinding and two-stage cleaning. In the initial set of tests, the 2nd cleaner concentrate was cyanide leached. After reviewing the data from those tests, cyanide leaching was refocused on the rougher and 1st cleaner scavenger tailing.

From these tests, recovery of Au in rougher flotation ranged from ~62% in ~15% mass in (Test F-2, P80 of ~103 μm) to ~69% in ~17% mass (Test F-1, P80 of ~128 μm). At the same mass pulls, Ag recovery ranged from 74% (F-2) to 85% (F-1). The addition of a dithiophosphate collector (Cytec A208) in Test F-5 further improved Au recoveries to 80.1 Au % at a mass pull of 14.6%.


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10.3.1.3KCA Batch Tests – Jan 2011

In December 2010, the laboratory facility of KCA in Reno, Nevada received material from the Hycroft project. Portions of the received material were combined as directed to generate six (6) composite samples for testing. Initial testwork was conducted by KCA and reported (PAX, pH, and Grind Flotation Kinetics Study, January 2011). Additional flotation tests were conducted with leach tests on the products.

10.3.1.4KCA Locked Cycle Tests – May 2011

Portions of the six (6) composites were combined to generate two (2) master composites, a Sulfide Master Composite, and a Mixed Master Composite. Additional flotation tests with leach tests on the tails were conducted using material from these composites.

10.3.1.5G&T Metallurgical Services Ltd. – Feb 2011

Five separate shipments of samples were received at G&T Metallurgical Services Ltd between August 31 and December 3, 2010. The samples consisted of half HQ core with a total estimated weight of about 2.9 tons. These samples were used to construct the thirty-nine composites that were used for flotation and cyanidation tests.

On the first set of twenty-four composites, a single batch cleaner flotation test was completed. On the second set of samples, M1 to M17, a much simpler flowsheet was applied, simplifying the reagent scheme to PAX and MIBC. The flotation froths obtained were more stable and more characteristic of a standard sulfide froth compared to the original flowsheet. The samples responded relatively well to flotation. For all thirty-nine samples, the flotation recoveries, on average, measured about 78 percent for Au and 67 percent for Ag to the rougher concentrate.

On average, the rougher recoveries using this revised flowsheet on M1 to M17 measured 78 percent for Au and 83 percent for Ag. These metal recoveries tended to track sulfide sulfur recovery to the rougher concentrate. Table 10-4 and Table 10-5 show the results of this testwork.


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Table 10-4: G&T Composites 1 through 24 Flotation Test Results


Sample ID	S(t) %	S(s) %	Au oz/ton	Ag oz/ton	Rougher Conc Weight Pull, %	Au Recovery to conc, %	Ag Recovery to conc, %	Type
G&T Composite 1	0.70	0.62	0.009	3.968	13.3	80.1	77.3	Sulfide
G&T Composite 2	2.48	2.49	0.145	11.136	13.2	79.6	63.2	Transition
G&T Composite 3	2.29	2.28	0.076	11.872	12.2	82.7	61.9	Transition
G&T Composite 4	1.25	1.22	0.008	18.016	9.1	60.4	27.7	Sulfide
G&T Composite 5	1.50	1.40	0.045	0.496	12.9	83.1	83.6	Sulfide
G&T Composite 6	1.64	1.51	0.027	23.136	15.0	88.3	72.6	Sulfide
G&T Composite 7	1.36	1.29	0.010	9.504	15.7	94.5	37.8	Sulfide
G&T Composite 8	1.33	1.26	0.027	4.000	13.1	89.4	50.5	Sulfide
G&T Composite 9	4.30	3.81	0.021	0.602	16.5	86.5	88.5	Sulfide
G&T Composite 10	2.23	2.04	0.014	1.946	11.6	80.5	60.1	Sulfide
G&T Composite 11	2.80	2.72	0.027	8.064	17.8	88.1	53.9	Transition
G&T Composite 12	1.57	1.25	0.113	1.680	8.3	73.6	44.8	Oxide
G&T Composite 13	2.32	2.02	0.065	1.472	11.6	56.1	68.2	Transition
G&T Composite 14	2.08	1.34	0.004	1.818	7.8	89.5	30.2	Sulfide
G&T Composite 15	1.78	1.71	0.043	5.376	10.8	94.0	63.2	Transition
G&T Composite 16	2.64	2.27	0.022	0.627	14.9	77.2	76.9	Sulfide
G&T Composite 17	0.45	0.34	0.093	0.198	5.2	28.1	27.5	Oxide
G&T Composite 18	1.33	1.08	0.014	0.074	11.8	58.7	61.2	Sulfide
G&T Composite 19	2.00	1.76	0.012	0.266	15.7	69.9	50.3	Sulfide
G&T Composite 20	13.70	11.80	0.045	0.992	31.2	93.7	87.1	Sulfide
G&T Composite 21	2.06	1.97	0.019	0.598	13.1	85.6	74.9	Sulfide
G&T Composite 22	1.73	1.70	0.025	0.464	13.1	61.2	60.7	Sulfide
G&T Composite 23	1.72	1.31	0.016	2.099	11.1	87.5	53.7	Sulfide
G&T Composite 24	2.00	1.92	0.024	3.584	15.5	85.4	38.9	Sulfide

Average Sulfides	2.56	2.25	0.020	4.246	14.2	80.7	60.7
Average All	2.39	2.13	0.037	4.666	13.4	78.1	58.9


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Table 10-5: G&T Composites M-1 through M-17 Flotation Test Results


Sample ID	S(t), %	S(s), %	Au, oz/ton	Ag, oz/ton	Rougher Conc Weight Pull, %	Au Recovery to conc, %	Ag Recovery to conc, %	Type
G&T Composite M-1	1.98	1.81	0.038	0.378	13.4	86.4	82.4	Sulfide
G&T Composite M-2	2.62	1.75	0.013	1.082	14.2	82.1	85.9	Sulfide
G&T Composite M-3	1.20	1.12	0.014	0.272	12.7	73.6	83.2	Sulfide
G&T Composite M-4	1.62	1.55	0.020	0.150	18.1	79.7	76.8	Sulfide
G&T Composite M-5	1.81	1.70	0.013	0.128	18.8	76.9	72.7	Sulfide
G&T Composite M-6	1.92	1.79	0.016	0.253	20.8	79.1	76.4	Sulfide
G&T Composite M-7	No Data
G&T Composite M-8	No Data
G&T Composite M-9	2.25	2.06	0.011	0.586	10.9	89.7	92.7	Sulfide
G&T Composite M-10	2.50	2.00	0.012	2.454	11.6	76.7	96.0	Sulfide
G&T Composite M-11	1.55	1.49	0.016	1.475	8.3	80.4	96.4	Sulfide
G&T Composite M-12	1.86	1.30	0.016	3.840	10.4	80.4	97.3	Sulfide
G&T Composite M-13	6.34	2.99	0.046	1.043	13.0	85.7	86.8	Sulfide
G&T Composite M-14	5.53	2.32	0.020	0.288	16.0	88.2	84.1	Transition
G&T Composite M-15	2.32	1.15	0.024	1.584	7.0	44.9	61.3	Oxide
G&T Composite M-16	2.51	2.43	0.017	0.486	14.3	74.6	87.8	Transition
G&T Composite M-17	1.52	1.39	0.017	0.259	16.1	65.1	62.8	Sulfide

Average Sulfides	2.26	1.75	0.019	0.993	14.0	79.7	84.1
Average All	2.50	1.79	0.020	0.943	13.7	77.6	82.8

10.3.1.6Hazen Research, Inc. – August 2011

For this investigation, 38 drill hole composite samples from five mineralized material types. Initially, flotation was performed with sodium hydrosulfide (NaHS) and copper sulfate (CuSO4). In subsequent tests, the NaHS and CuSO4 were eliminated and lead nitrate (Pb(NO3)2) was added as a modifying agent. The pH ranged from neutral to 10.5, after modifying agents were used. The redox potential was also monitored.

A series of 91 small-scale flotation experiments was performed on 4.4-lbs splits from the 38 composites. The objective of the flotation work was to define the variability among the composite samples.

The next 41 small-scale flotation experiments were performed on Composites 1–38, except for Composites 6, 8, 9, and 10, using rougher flotations following G&T Metallurgical conditions and conditions recommended by Hazen. Rougher weight pulls ran from 4.9% to 30.7%, with Au and Ag recoveries running from 26.9% to 97.6% and 17.1 to 98.7%, respectively.

The rougher concentrate assays ranged from 0.032 oz/ton Au (Test 3346-82) to 1.536 oz/ton Au (Test 3346-40) and from 0.224 oz/ton Ag (Test 3346-82) to almost 73.601 oz/ton Ag (Test 3346-68). The Au and Ag recovered in the rougher concentrates ranged from 27% (Test 3346-52) to 91% (Test 3346-68) and from 17% (Test 3346-52) to almost 99% (Test 3346-68), respectively.

10.3.1.7Fitness of Grind for Flotation Tests

Most flotation tests on Hycroft samples were performed on materials that were ground at 80 percent finer than 100 microns. Several other tests were also conducted at finer and coarser grinds. The general trend indicates that flotation can achieve good recoveries at grinds ranging from 100 to 150 microns. Recoveries tended to decrease with grinds finer than 100 microns or coarser than 150 microns.


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10.3.1.8Reagent Suite

Both G&T and Hazen concluded that flotation tests using NaHS as a sulfurizing agent, as well as tests done at alkaline pH, generally performed poorly.

The exploratory and variability flotation test results presented above showed that sulfide mineralized materials can be floated for Au and Ag. The reagents used were strong, non-selective sulfide collectors. Frothing was achieved with either methyl isobutyl carbinol (MIBC) or Dowfroth 250 (DF250), or both. Table 10-6 summarizes the reagent schemes applied by G&T, SGS, and Hazen. In all laboratory tests, the reagent dosages were high.

Table 10-6: Flotation Reagent Schemes Studied


Reagent, lb/ton	Laboratory
	G&T	Hazen	SGS
NaHS		0, 2.56	2.1
PAX	0.552	0.546, 0.416	0.21
3418A		0, 0.064-0.124	0.055
MIBC	0.05-0.128, 0.192	0.02-0.064
DF250		0.02-0.064	0.095

Based on the results of tests from the three laboratories, particularly G&T, the simple reagent scheme can be further developed. Several tests indicate Cytec’s AEROPHINE 3418A Promoter (sodium diisobutyldithiophosphinate) may improve Au and Ag recovery.

10.3.2Flotation Time

Flotation kinetics were not systematically studied when the flotation tests were being conducted. However, flotation data from the G&T work on M Composites included recoveries from froth collected at 4, 8, 12, and 16 minutes. Fifteen rougher flotation tests were performed. Kinetics plots for Au and Ag from this work are shown in Figure 10-1, which shows only a few data points to avoid clutter, but shows the recovery curves fitted to the data points by asymptotic curve fitting.

From each of the 15 sets of data, the maximum recovery, Rmax and kinetics constant, K were derived from the asymptotic lines.


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Figure 10-1: Recovery vs. Time Plot, G&T Kamloops Tests, M Composites

Source: Figure prepared by M3, 2016.

The results show that the average laboratory flotation time required to attain 95% of the maximum recovery is 19 minutes for gold and 17 minutes for silver.


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10.4Direct Cyanidation

Direct cyanidation of concentrate bulk samples (P80 = 325 mesh, or 44 microns) taken from all zones of the deposit were conducted early on in 2010. These tests yielded poor results with recoveries from Brimstone and Vortex samples in the mid-20% range for Au and 80% range for Ag, while the other samples yielded recoveries ranging from 45 to 50% for Au and 55 to 83% for Ag.

A good measure of recovery by direct cyanidation is the ratio of cyanide soluble metal to the total assay of the metal, that is, AuCN/AuFA and AgCN/AgFA. These ratios have been determined for a large number of exploration samples and have been included in the resource database. The cyanide soluble ratios for Au have been utilized in resource estimation, particularly to route certain minerals with higher cyanide soluble Au to the heap leach pad.

10.5Concentrate Oxidation Tests

Oxidation tests on Hycroft concentrates included POX, roasting, atmospheric oxidation, and other oxidation methods. The results indicated that all these processes would work, with varying degrees of recovery. The following is a summary of the results of these tests.

In 2007, Hycroft began to explore milling options to expand production by processing their refractory sulfide mineralized materials. This included the production of flotation concentrates followed by oxidative treatments of the concentrates. The focus of this testwork was primarily on oxidation methods typically employed in the gold industry for refractory mineralized materials, POX, and roasting.

In 2012, Hycroft tested a suite of alternative oxidation methods, including chlorination, atmospheric alkaline oxidation, and fine-grinding with intense cyanidation. The goal was to develop an economically viable process that would be less expensive to build and operate than a POX autoclave facility. Initial results were positive; indicating that the Hycroft rougher concentrates were amenable to oxidation under atmospheric conditions, using trona as the acid neutralizing agent. Pilot plant testing was conducted on three main domains to confirm these results at Hazen Research Inc.

In 2016, Hycroft began developing an AAO demonstration plant at the mine site utilizing trona to process 100% of the flotation concentrates and produce doré onsite. Accounting for the historical and current performance of the oxide heap leach operations, oxide heap leach metallurgical testing combined with results from all bench-scaled tests, pilot and demonstration plant Mill-AAO metallurgical testing, the individual process recoveries for each processing stream for Au and Ag were calculated and are presented in Table 10-7. This was the basis for the NI 43-101 Feasibility Study Technical Report published in 2016 (Ibrado, A. et al, 2016).

Table 10-7: Estimated Metallurgical Recoveries from 2016 Feasibility Study – Au and Ag


	Au			Ag
	Contained koz	Recovered koz	Recovery (%)	Contained koz	Recovered koz	Recovery (%)
Heap Leach	3,875	1,933	49.9	21,242	21,242	15.5
Mill-AAO Sulfide	7,797	5,696	73.0	287,693	287,693	81.6
TOTAL	11,672	7,629	65.4	489,447	308,935	63.1

10.5.1Atmospheric Oxidation – Batch Tests

The focus of testing over the years 2013 through 2016 was to develop a process to oxidize sulfide concentrates under atmospheric conditions. The process was envisioned to be conducted in an agitated slurry at elevated temperatures, using oxygen as the oxidant and trona as the neutralizing agent for the acid produced. Several batch oxidation tests using trona were done at Hazen under various conditions on concentrates from Central, Brimstone, and Vortex composites.

Batch tests using trona showed that full oxidation is not required to attain high recoveries in subsequent cyanide leaching, consistent with the findings of earlier oxidation studies. About 85% of the Au and 92% of the Ag can be recovered by cyanidation if 60% of the sulfide-sulfur content in the concentrate is oxidized. The results for Au are shown in Figure 10-2.


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Figure 10-2: Au and Ag Extraction vs. Sulfide Oxidation

Source: Figure prepared by M3, 2019.

The reaction kinetics were also found to be improved by higher temperatures up to 167ºF. Higher reaction temperatures (around 194ºF) were tested but returned slower oxidation kinetics, perhaps due to the decreased oxygen solubility in the laboratory bench-scale setting.

10.5.2Pilot Plant Oxidation Tests

Continuous pilot tests in 10-liter vessels were completed at Hazen for the three domains. The results confirmed the findings of the batch tests. The pilot plant tests were run using 600 lbs of trona per ton of concentrate, at 167°F, 25- micron grind size, 20% solids and 48 hours total residence time. Different material types oxidized at varying rates, with Vortex materials oxidizing the fastest followed by Central and then Brimstone. The Master Composite oxidation rate was comparable to Brimstone.

•Au recovery versus sulfide oxidation was better than anticipated from bench-scale tests;

•80% Au recovery achieved at 50% sulfide oxidation for all material types;

•87% Au recovery achieved at 60% sulfide oxidation for all material types.

10.5.3Hycroft Mill Demonstration Plant

Hycroft Mining built a demonstration plant with nominal capacity of 10 ton/d at the Hycroft mine site. The plant consisted of a ball mill, a rougher flotation bank, concentrate and tailing thickeners, a regrind mill, oxidation tanks, neutralization tanks, an oxidized concentrate thickener, cyanide leach tanks, CCD thickeners, and a Merrill-Crowe precipitation package. It was operated continuously as an integrated plant, with concentrate surge capacity before oxidation and a pregnant solution storage before Merrill-Crowe. A report on the results of conclusions from the demonstration plant was presented in 2019 (M3 Engineering & Technology et al., 2019).

The demonstration plant was operated with Central and Brimstone materials that were mined from exposed mineralization at the surface of the current open pit.

Highlights of the demonstration plant test results are shown in Figure 10-3 for Central materials. For clarity, only results from Tank 1 (TK1) and Tank 5 (TK5) are shown. Oxidation levels of 60% or better were achieved when the correct steady- state testing conditions were maintained.


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Figure 10-3: Oxidation of Central Flotation Concentrate: Sulfate Spike Test

Source: Figure prepared by M3, 2019.

Once the concentrates were oxidized, Au and Ag recoveries significantly improved over the direct cyanidation recoveries. The results of cyanide leaching of oxidized concentrate are shown on Figure 10-4 as recovery of Au and Ag during the demonstration plant operation. The graph starts with Central concentrate and then switches to Brimstone concentrates on 6/11/2016. Recovery of Au and Ag from Central concentrate peak at around 85%. Au recovery from Brimstone reaches 80 percent while Ag recoveries from Brimstone peaked at 90%. The general shape of the lines roughly follows the degree of oxidation of the concentrate.

Figure 10-4: Demonstration Plant Cyanide Leach Recovery of Au and Ag

Source: Figure prepared by M3, 2019.

10.5.4Pressure Oxidation

Previous POX testwork was performed primarily by Hazen and SGS on various flotation concentrates of Hycroft sulfide mineralized materials samples, composites thereof and two transition samples. POX testwork has also been performed by Hazen and SGS under both alkaline and acidic environments.


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The following is a list all POX testwork reports provided to Ausenco:

•Hazen Project 11232 Report and Appendices A-F, -POX-CIL Evaluation of Hycroft Flotation Concentrates.

•Hazen Project 11243-01 Report and Appendix, -Evaluation of Hycroft Blend Flotation Concentrate.

•Hazen Project 11307 Report and Appendix, -Evaluation of Kappes, Cassiday & Associates Flotation Concentrate.

•SGS Project 13224-001/003 Final Report, -An Investigation into Oxidative Pre-treatment of Hycroft Flotation Concentrates.

•SGS Hycroft Project – 12012-001 Report 3, -The Recovery of Au and Ag from Hycroft Project Sulfide Samples, Allied Nevada Gold Corporation.

•Kappes, Cassidy & Associates Project No. 189 C,-Hycroft Pressure Oxidation and Leach Testwork.

Previous testwork on alkaline POX had been conducted on flotation concentrates. Table 10-8 summarizes the alkaline POX test results conducted by Hazen, SGS.

The results indicate that: 1) an operating temperature range of 212° F to 437°F; 2) 40 psi oxygen overpressure; and 3) 240 minutes to 360 minutes’ residence time. The limited dataset for alkaline POX indicated poorer gold and silver recoveries.

Table 10-8: Hycroft Alkaline POX Testwork Summary


Flotation Concentrates Samples	Sulfide (Stotal) wt%	Au ppm	Ag ppm	AC Temp °F	Solids wt%	AC Retention Time min	Oxygen Over-pressure Psig	Caustic Consumption lb/ton	NaCN Consumption (lb/ton)	Au recovery %	Ag recovery %
Brimstone	40.1	11.6	418	437	20	256	40	5.42	1.6	98.5	72.9
	40.1	11.6	418	212	40	360	40	6.06	6.8	54.3	71.2
Hycroft Blend Float Concentrate	38.5	18.1	2103	437	26	240	40	0.15	0.2	64.3	35.8
	38.5	18.1	2103	437	26	240	40	1.46	1.6	63.8	52.0
	38.5	18.1	2103	437	26	240	40	2.95	3.3	63.8	82.1

Previous testwork on acid POX had been conducted on flotation concentrates to determine operating criteria. Table 10-9 summarizes the acid POX test results conducted by Hazen, SGS and KCA.

The results indicate that: 1) an operating temperature range of 374°F to 437°F; 2) 100 psi oxygen overpressure; and 3) 60 minutes’ residence time produce the highest cyanide amenability for Au and Ag recovery. The POX tests also indicate that the concentrates may be prone to form jarosites, which inhibits Ag recovery. The evidence for jarosite formation is:

•Color of the acidic autoclaved pulp is yellow on discharge and reddish brown when conditioned with a lime boil.

•Ag recovery is higher when the pulp is treated with a lime boil, a procedure which subjects the hot pulp for several hours to alkaline conditions.

The gold and silver recoveries from rougher concentrate POX discharge material that has been lime boiled and then leached with cyanide was in the mid-90s and 80s, respectively (Table 10-9).


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Table 10-9: Hycroft Acid POX Testwork Summary


Sulfide Concentrate Samples Tested	Sulfide (S=) wt%	Au ppm	Ag ppm [1]	Temp °F	Solids wt%	Autoclave retention time (min)	Oxygen Over-pressure PSIG	Lime Boil Time hr	Cyan. Conc. ppt [6]	Sulfide Oxidation %	Au recovery %	Ag recovery %	Test Lab
Brimstone	40.1	11.6	418	374	20	60	100	2	1	-	97.5	89	Hazen
Cut 4	36.9	11.4	168	374	20	60	100	2	1	-	94	94.1	Hazen
Camel	37.7	9.33	152	374	20	60	100	2	1	-	97.7	89.9	Hazen
Bay	22.1	6.03	52.3	374	20	60	100	2	1	-	97.5	75.3	Hazen
Bone Yard	31.9	5.97	95.3	374	20	60	100	2	1	-	96	86	Hazen
Hycroft Blend	38.5	18.1	2103	401	15	60	100	2	1	-	100	77.1	Hazen
Sulfide Master Ro	18.9	4.9	432	401	15	60	100	6	1	-	87	65.8	Hazen
Mixed Master Ro	9.3	8.5	193	401	15	60	100	6	1	-	82.8	86.4	Hazen
Central Blk Sul Ro	8.4	2.47	26	374	20	60	100	2	1	98.8	93.6	90.5	SGS
Central Blk Sul Cl	35.6	10.1	131	374	20	60	100	2	1	99.8	94	94.2	SGS
Vortex Blk Sul Ro	9.1	2.93	276	374	20	60	100	2	1	98.6	97.7	73.5	SGS
Vortex Blk Sul Cl	32.3	10.8	976	374	20	60	100	2	1	99.8	96	72.2	SGS
Central Sul Cl	30.7	10.3	750	374	20	60	100	2	1	98.1	93.5	81.9	SGS
Brimstone Sul Cl	34.7	7.93	392	374	20	60	100	2	1	83.6	53.6	49.5	SGS
Vortex Sul Cl	35.4	8.03	350	374	20	60	100	2	1	94.2	94.5	89.2	SGS
POX 1 Cl con F-16 [2]	31.1	5.93	158	437	8.1	90	100	0-3	1	98.8	71.8	5.5	SGS
POX 2 Cl con F-25 [3]	33.9	9.38	155	437	8.2	90	100	0-3	1	98.6	64.3	19.1	SGS
POX 3 Cl con F-26 [4]	24.2	4.95	165	435	9	90	100	0-3	1	97.6	72.7	72.7	SGS
Brimstone Sul Cl [5]	33.9	7.13	383	428	30	300	100	2	2	99.9	94	97	KCA
[1] Fire Assay
[2] No lime boil, no NaCl
[3] No lime boil, 1.34 oz/g NaCl
[4] No lime boil, 2.67 oz/g NaCl
[5] H2SO4 added to autoclave feed
[6] ppt parts per thousand

Acid POX followed by lime boil was evaluated in the development of the mineral resource, in part, due to the ability to consistently achieve sulfide oxidation. Sulfide oxidation through POX is expected to be consistently above 95% whereas sulfide oxidation through AAO did not consistently achieve the 60% target (Figure 10‑3). Therefore, gold and silver recoveries from POX residue would be higher and more stable compared to AAO. Other reasons for evaluating POX included:

•Acquiring trona in quantities required to operate an AAO circuit was problematic.


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•Limestone is a more cost-effective reagent for acid neutralization.

•Cyanide consumption after pressure oxidation is reduced compared to AAO.

Soda ash was considered as an alternative to trona but was less cost effective than limestone.


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10.5.5Roasting

Roaster testwork was conducted on the Brimstone concentrate from a pilot plant to determine optimum conditions for processing. The results indicate that the optimum roast temperatures are between 797°F and 842°F.

During the tests, average recoveries of 89% Au and 74% Ag were achievable from the concentrates by varying the leach and roast conditions slightly for the majority of the concentrate produced.

10.6Solid-Liquid Separation Tests

Several thickeners are included in the Hycroft flowsheet. New settling tests for these thickeners were performed by Pocock Industrial, Inc. Samples tested were taken from the hydrometallurgical process development studies for Hazen Research, Inc.

Sample streams, namely:

•Rougher flotation concentrate;

•Neutralized AAO circuit product (pre-leach);

•Cyanide-leached slurry (feed to CCD); and

•Rougher flotation tailing.

A summary of the settling test results is presented in Table 10-10 below.

Table 10-10: Settling Test Results

Sample

Tested Feed Solids (%)

Design Basis Net Feed Loading ft2/gpm

Flocculant Dosage lb/ton

Predicted Underflow Density % solids

Overflow Clarity, ppm TSS

Rougher Concentrate

7.47 – 14.79

0.87 – 1.37

0.12 – 0.13

40.6 – 49.1

150 – 318

Pre-Leach Oxidized Concentrate

7.52 – 7.75

0.68 – 0.92

0.11 – 0.17

35.0 – 41.0

150 – 329

CCD Feed

7.41 – 8.00

0.92 – 1.11

0.15 – 0.17

33.0 – 37.0

150 – 349

Rough Tails

14.10 – 15.80

0.84 – 0.88

0.07 – 0.13

59.5 – 65.0

150 – 250


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11MINERAL RESOURCE ESTIMATES

Mineral resources for the Mine were developed using conventional block modeling methods and open pit optimization software to estimate the component of mineralization that has reasonable prospect of economic extraction. The mineral resource was developed in accordance with the U.S. Securities and Exchange Commission Rule SK-1300 for Mineral Projects. This work was completed by IMC with John Marek P.E. acting as the Engineer of Record.

The model was assembled to support mine planning and production prediction for the Hycroft initial assessment presented in this text. As a result, the model of in-situ mineralization will be used to develop the mineral resources.

11.1Model Location

The block model is assembled in the local mine grid that has been in place for a number of years at Hycroft. That grid is rotated 16 degrees (right rotation looking down) compared to true north. Table 11-1 summarizes the block size and block limits.

Table 11-1: Block Size and Model Size


Model Location	From Coordinates	To Coordinates	Number of Blocks
Easting Limit	13,000	26,000	325
Northing Limit	35,440	54,800	484
Elevation Limits	2,200	6,600	110
Block Size			40 x 40 x 40 ft

Note: Coordinates are the outside edges of the blocks. The model is assembled in the mine grid.

The drillhole database and the block model are all in the mine grid. To the user, there does not appear to be a rotation because the mine grid is treated as if there were no rotation. The block size selection will be discussed in a later sub-section.

11.2Database

The drillhole database was assembled over many years by multiple companies using at least four different drill methods. That history and the verification of the historical information has been discussed in previous sections.

As noted previously, the Au assay values in the Hycroft legacy database prior to 2000 were historically factored upward by a factor of 1.19. Prior to resource model estimation, that factor was removed by multiplying all gold assays prior to 2000 by 1/1.19 = 0.8403. The removal of the factor does not have substantial impact on the deeper sulfide component of the deposit, but it does remove an observed bias in the near surface data.

There are stockpiles and historical leach pads at the Mine that are within the block model area. Many of those have been drilled after the original excavation of hard rock by sonic or rotary methods. The stockpile holes have been used to estimate the stockpile and leach pad areas, they have not been used to estimate in-situ rock. In total, the Hycroft database contains 5,377 drillholes with 500,960 sample intervals. Within the area of the block model, there are 5,323 drillholes with 493,357 drill intervals amounting to 2,838,923 ft of drilling. Table 11-2 summarizes the amount of drilling and assay information that was used to assemble the block model.


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Table 11-2: Data Available for the Assembly of the Resource Model for Au, and Ag


Number of	Total in Model	Stockpile Drilling	In-Situ Rock Drilling	Total In-Situ Rock Remaining After 31 Jan ‘21
Holes	5,323	134	5,189	4,593
Assay Intervals	493,357	2,126	491,231	363,910
Au Fire Assays	365,131	1,939	363,192	262,552
Au Cn Assays	208,699	1,708	206,991	123,622
Ag Fire Assays	118,618	1,729	116,889	102,518
Ag Cn Assays	284,654	1,877	282,777	209,248

Although all of the in-situ rock drilling was used to estimate the in-situ rock, the last column indicates how much of the information remains in the ground after January 31, 2021.

Sulfide sulfur and mercury were estimated from separate databases. A set of sample composites were established by weighing pulp material from the drillholes. Specific holes were selected to provide coverage over the zone of the deposit being considered for flotation mill treatment. Those holes were analyzed by LECO methods to determine sulfide sulfur on 25 ft downhole composites. The separate LECO composite database was used to estimate sulfide sulfur within the block model. There are 150 drillholes within in-situ rock that contain 5,311 composite values for sulfide sulfur in the LECO database.

Mercury was sampled as part of an ICP program with 7,306 composite intervals from 373 drillholes with nominal composite length of 40 ft. There are 6,738 intervals from that data set assayed for mercury by ICP methods.

11.3Basic Statistics

The assay values of economic interest at the mine are gold, silver, and sulfide sulfur. Sulfide sulfur has an impact on the operating cost of the concentrate treatment plant. In addition, the cyanide soluble assays of Au and Ag are of interest because they provide a basis to establish the best metallurgical process based on the ability of Au and Ag to dissolve into cyanide solution.

Table 11-3 presents the basic statistics of the assay database used to assemble the model. The lower portion of the table illustrates the amount of data remaining in the ground after January 31, 2021. The stockpile assays are not included in the table. The entire database was searched for grade estimation purposes, but practically, the data in the lower half of the table remaining in ground after January 31, 2021 is indicative of the amount of information available to estimate the remaining Mineral Resource.


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Table 11-3: Assay Database (No Stockpile Assays)

Commodity

Number of Assays

Mean Grade

Standard Deviation of Grade

Maximum Value

Fire Au

363,192

0.009 oz/ton

0.017 oz/ton

3.150 oz/ton

Includes historical up factor of pre-2000 drilling

Fire Au Unfact

363,192

0.008 oz/ton

0.016 oz/ton

3.150 oz/ton

Fire Au Factor of pre-2000 drilling removed above

Cyanide Sol Au

206,991

0.006 oz/ton

0.023 oz/ton

8.000 oz/ton

Cn Au/FaAu

190,714

0.52

0.34

1.00

Fire Ag

116,889

0.51 oz/ton

3.07 oz/ton

647.50 oz/ton

Cyanide Sol Ag

282,777

0.12 oz/ton

0.38 oz/ton

62.51 oz/ton

Sulfide Sulfur

5,311

1.79%

1.40%

25.12%

From LECO database

Assay information remaining below the January 31, 2021 topography surface

Commodity

Number of Assays

Mean Grade

Standard Deviation of Grade

Maximum Value

Fire Au

262,552

0.009 oz/ton

0.016 oz/ton

3.150 oz/ton

Includes historical up factor of pre-2000 drilling

Fire Au Unfact

262,552

0.008 oz/ton

0.016 oz/ton

3.150 oz/ton

Fire Au Factor of pre-2000 drilling removed above

Cyanide Sol Au

123,622

0.005 oz/ton

0.026 oz/ton

8.000 oz/ton

CnAu/FaAu

110,801

0.42

0.33

1.00

Fire Ag

102,518

0.53 oz/ton

3.26 oz/ton

647.50 oz/ton

Cyanide Sol Ag

209,248

0.12 oz/ton

0.42 oz/ton

62.51 oz/ton

Sulfide Sulfur

5,311

1.79%

1.40%

25.12%

From LECO data base

Table 11-3 illustrates the impact of removing the Au grade factor that has historically be applied to the pre-2000 drilling. Of the 262,552 Au assays remaining in the ground after January 31, 2021, 73,003 assays or 28% of the remaining Au database has had the 1.19 up factor removed.

Table 11-3 also illustrates that Au cyanide soluble assays exist on roughly 47% of the database. Ag fire assays exist on only 39% of the remaining database. During leach operations, cyanide Ag assays were routinely completed, however total Ag assays were not common. Estimation of total or fire Ag will consequently be limited by the smaller number of available assays.

Since 47% of the data have received cyanide Au assays, the ratio of cyanide Au / fire Au was estimated rather than cyanide Au directly. Although not statistically optimum, the process is necessary and common in the industry. The ratio of cyanide soluble Au to fire assay Au (CnAu/FaAu = Cnratau) is used during mine planning to allocate material to the proper treatment process. When the Cnratau is calculated, values over 1.0 are set back to 1.0. The basic statistics of the Cnratau is also summarized on Table 11-3.

11.3.1Geology

The geology of the Hycroft deposit has been presented in previous report sections. The primary occurrences which have control on the grade distribution at Hycroft are Lithology, Alteration, and Structure. Each have impacts on mineralization.

11.3.2Lithology

The main lithology or rock types in the Hycroft deposit are:

•Alluvium


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•Tuffaceous Lake Bed Sediment, Part of the Tertiary Sulfur Group

•Camel Conglomerate. Part of the Tertiary Sulfur Group, and eroded from the Kamma Volcanics

•Kamma Volcanics, Tertiary, but older than the sulfur group conglomerates and sediments.

•Auld Lang Sign (ALS)

•Jurassic laminated siltstone, the basement of the deposit.

The Alluvium is typically barren and has not had grade assignment within the model. The primary mineral deposits are the Camel and Kamma units. There is minor mineralization in the ALS but since there is little drilling it has not been estimated in this resource model.

Interpreted solids representing the above rock types were provided by Hycroft and checked against logging by IMC. IMC found them appropriate for use in development of the resource model. Figure 11-1 is an east–west cross-section illustrating the major rock types looking north.

Assay values were back coded from the lithology solids prior to boundary analysis.

11.3.3Alteration

Alteration consists of:

•Argillic;

•Silicic; and

•Propylitic.

Hycroft provided alteration solids to IMC. IMC checked those solids against the logged database and found them to be acceptable for use in development of the resource model. In summary, when propylitic alteration was encountered, boundary analysis and basic statistics indicated that it was statistically similar to the argillic altered material, and it was combined with argillic during block grade estimation.

Silicic alteration is prevalent and tends to be deeper and generally more prevalent in the eastern portion of the deposit. Boundary and statistical analysis indicates that the silicic altered material is generally higher grade than the argillic-propylitic altered rock. Figure 11-2 is an east–west cross-section through the interpreted alterations, looking north.

Assay values were back coded from the alteration solids prior to boundary analysis.

11.3.4Structure

Several north–south striking basin and range faults cut through the Hycroft deposit. In addition to the northeast striking, the deposit is cut by the Ramp Fault and the West dipping East Fault. The East Fault is interpreted to be a thick shear zone and appears to the orientation and possibly the conduit of mineralization in the eastern portion of the deposit. The footwall of the East Fault has minor mineralization, but grades were not estimated in the footwall within this model.

Figure 11-3 is a map view of the faults and the numbering system assigned by IMC to the fault blocks between the faults. The fault block numbers will be used to define the domains and search parameters for block grade estimation.

Assay values were back coded from the structure block solids prior to boundary analysis.


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Figure 11-1: East–West Cross-Section 43,000N Looking North, showing Hycroft Rock Types

Source: Figure prepared by IMC, 2022.

Figure 11-2: East–West Cross-Section 43,000N Looking North, showing Hycroft Alterations

Source: Figure prepared by IMC, 2022.


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Figure 11-3: Hycroft Structure Interpretation

Source: Figure prepared by IMC, 2021.


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11.4Domain

Domains for grade estimation are a combination of structure, alteration, and lithology. The domain boundaries were developed by studying the basic statistics and by performing boundary analysis between contacting structural domains.

Boundary analysis selects the assay (or composite) information from both sides of the boundary being tested at several different separation distances. IMC then completes a series of statistical hypothesis tests to confirm if the data on either side of the boundary could have come from the same or different statistical populations.

As a result of the fairly extensive boundary analysis, IMC arrived at 14 domains, primarily based on the results analyzing the Au assay information.

The domains are summarized on Table 11-4.

Table 11-4: Population Domains for Grade Estimation

Population Domain Number

Alteration Type and Code

Lithology Type and Code

Structure

Block

Code

Description

Acid Lch 501

All

Acid Leach Alteration

Arg+Prop 502+504

Tsg 4

All

Argilic Lake Sediments

Silicic 503

Tsg 4

All

Silicic Lake Sediments

Arg+Prop 502+504

All

Argillic West of the Range Fault

Arg+Prop 502+504

All

101

Argillic Between Range and West Splay

Arg+Prop 502+504

All

102

Argillic Between West Splay and Central

Arg+Prop 502+504

All

203, 204

Argillic Between West Splay and Central South

Arg+Prop 502+504

All

104, 105, 201, 202, 205, 207, 501

Argillic Between Central Fault and East Footwall

Silicic 503

All

Silicic West of the Range Fault

Silicic 503

All

101

Silicic Between Range and West Splay

Silicic 503

All

102

Silicic Between West Splay and Central

Silicic 503

All

203, 204

Silicic Between West Splay and Central South

Silicic 503

All

104, 105, 201, 202, 205, 207, 501

Silicic Between Central Fault and East Footwall

All

Alluvium, not estimated

11.5Assay Caps

Prior to grade estimation, high-grade outliers were capped to limit undue impact on block grade estimation. Cumulative frequency plots were studied within each of the domains in order to set cap values. In all cases only a small percentage of high valued samples were capped, generally less than 0.5% of the database. Table 11-5 summarizes the cap values that were applied to assays prior to calculating composites.


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Table 11-5: Assay Cap Values


Population Domain Number	Alteration Type and Code	Lithology Type and Code	Structure Block Code	Description	Assay Cap Value
					Au* oz/ton	Ag oz/ton	Cn Ag oz/ton
1	Acid Lch 501	All	All	Acid Leach Alteration	0.150	4.00	2.00
2	Arg+Prop 502+504	Tsg 4	All	Argillic Lake Sediments	0.045	0.60	0.40
3	Silicic 503	Tsg 4	All	Silicic Lake Sediments	0.025	0.70	0.40
4	Arg+Prop 502+504	All	10	Argillic West of the Range Fault	0.037	1.50	0.90
5	Arg+Prop 502+504	All	101	Argillic Between Range and West Splay	0.060	0.35	0.12
6	Arg+Prop 502+504	All	102	Argillic Between West Splay and Central	0.120	0.80	0.70
7	Arg+Prop 502+504	All	203, 204	Argillic Between West Splay and Central South	0.120	10.00	3.00
8	Arg+Prop 502+504	All	104, 105, 201, 202, 205, 207, 501	Argillic Between Central Fault and East Footwall	0.300	50.00	9.00
9	Silicic 503	All	10	Silicic West of the Range Fault	0.030	50.00	3.00
10	Silicic 503	All	101	Silicic Between Range and West Splay	0.083	4.50	1.50
11	Silicic 503	All	102	Silicic Between West Splay and Central	0.200	20.00	2.80
12	Silicic 503	All	203, 204	Silicic Between West Splay and Central South	0.250	90.00	9.00
13	Silicic 503	All	104, 105, 201, 202, 205, 207, 501	Silicic Between Central Fault and East Footwall	0.300	45.00	9.00
14	All	2	All	Alluvium, not estimated

*Gold assays are after the pre-1999 factors have been removed

The gold cyanide to fire assay ratio was capped at 1.0 to assure that there were no values with cyanide assay greater than fire assay when estimating the model.

In all cases above, the sonic drilling and the drilling in the Crofoot leach dump were excluded from the analysis as they do not represent in-situ mineralization.

11.6Bench Height Confirmation

Prior to compositing, a test was completed to confirm the selection of bench height for the model. The assay database was composited to alternative bench height intervals of 20 ft to 45 ft in 5-foot intervals. For each set of composites, the number of composites above cutoff and the average grade of those composites above cutoff were calculated. The number of composites multiplied by the average grade is used as an approximation of contained metal above cutoff. Multiple cutoffs of 0.002, 0.003, 0.004, and 0.005 oz/ton Au were tested at each of the bench heights. The sonic drilling and Crofoot leach pad drilling were not included.

The resulting graph is shown on Figure 11-4. Each line represents a different cutoff grade. The graph indicates that a bench height of 35 ft could result in a slight improvement in the recovery of Au compared to other tested heights.


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Figure 11-4: Bench Height Analysis

Source: Figure prepared by IMC, 2021.

The improvement at 35 ft would be between 0.3 and 1.1% difference in recoverable metal compared to the current operating 40 ft bench. Considering the production rate and the impact to change the current operation, the improvement due to 35 ft benches was not sufficient to warrant a change to the current operational practice of 40 ft.

11.7Composites

The assay data was composited to 40 ft downhole or length composites for input to grade estimation. The compositing was applied to the capped grades noted in a previous sub-section. Lithology, alteration, and structure block were assigned to each 40 ft composite on a majority basis. Lithology, alteration, and structure block were not respected in the composite process allowing composites to straddle a boundary. Table 11-6 summarizes the basic statistics of the composited assay data.


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Table 11-6: Basic Statistics of 40-ft Length Composites


Population Domain Number	Alteration Type and Code	Lithology Type and Code	Structure Block Code	Description	Statistics Summary for 40-ft Composites
					Statistic	Au* oz/ton	Ag oz/ton	Cn Ag oz/ton	CnAu/ FaAu Ratio
1	Acid Lch 501	All	All	Acid Leach Alteration	N = Mean = Std = Max =	4,970 0.0046 0.0067 0.1000	293 0.2987 0.3641 2.9454	4,491 0.0278 0.0624 1.1740	3,511 0.7568 0.2125 1.0000
2	Arg+Prop 502+504	Tsg 4	All	Argilic Lake Sediments	N = Mean = Std = Max =	253 0.0023 0.0032 0.0155	84 0.2099 0.9657 0.5023	250 0.0012 0.0023 0.1824	22 0.3983 0.2440 0.8566
3	Silicic 503	Tsg 4	All	Silicic Lake Sediments	N = Mean = Std = Max =	55 0.0039 0.0043 0.0140	20 0.2116 0.1312 0.4844	28 0.0649 0.0517 0.1916	14 0.2008 0.1225 0.4536
4	Arg+Prop 502+504	All	10	Argillic West of the Range Fault	N = Mean = Std = Max =	304 0.0033 0.0043 0.0244	123 0.1069 0.1425 0.8970	150 0.0331 0.0608 0.4764	45 0.5005 0.2868 0.9762
5	Arg+Prop 502+504	All	101	Argillic Between Range and West Splay	N = Mean = Std = Max =	386 0.0112 0.0092 0.0380	32 0.0097 0.0752 0.2460	35 0.0137 0.0242 0.1136	308 0.4924 0.2218 1.0000
6	Arg+Prop 502+504	All	102	Argillic Between West Splay and Central	N = Mean = Std = Max =	2,328 0.0094 0.0096 0.0951	155 0.1759 0.1618 1.6550	798 0.0388 0.0782 1.3478	2,006 0.6392 0.2542 1.0000
7	Arg+Prop 502+504	All	203, 204	Argillic Between West Splay and Central South	N = Mean = Std = Max =	2,333 0.0058 0.0080 0.0895	294 0.3253 0.4256 3.8306	1,700 0.0563 0.1156 1.4295	1,021 0.5693 0.2935 1.0000
8	Arg+Prop 502+504	All	104, 105, 201, 202, 205, 207, 501	Argillic Between Central Fault and East Footwall	N = Mean = Std = Max =	5,366 0.0055 0.0081 0.2246	1,446 0.4310 0.9651 17.2228	4,816 0.0705 0.1906 4.3843	1,643 0.4984 0.3094 1.0000
9	Silicic 503	All	10	Silicic West of the Range Fault	N = Mean = Std = Max =	917 0.0056 0.0055 0.0226	420 0.3581 1.0140 13.9026	467 0.1047 0.2225 2.0536	122 0.3550 0.2964 0.9861
10	Silicic 503	All	101	Silicic Between Range and West Splay	N = Mean = Std = Max =	367 0.0126 0.0118 4.5000	78 0.1721 0.2451 1.6540	70 0.0856 0.1031 0.5361	288 0.4895 0.2404 1.0000
11	Silicic 503	All	102	Silicic Between West Splay and Central	N = Mean = Std = Max =	3,741 0.0122 0.0102 0.1200	668 0.2268 0.3762 6.4105	1,329 0.0838 0.1139 1.2165	3,260 0.5495 0.2340 1.0000
12	Silicic 503	All	203, 204	Silicic Between West Splay and Central South	N = Mean = Std = Max =	6,409 0.0102 0.0094 0.1891	1,753 0.4253 1.0252 25.9226	5,287 0.1155 0.1923 4.7884	3,659 0.4689 0.2622 1.0000
13	Silicic 503	All	104, 105, 201, 202, 205, 207, 501	Silicic Between Central Fault and East Footwall	N = Mean = Std = Max =	15.505 0.0093 0.0086 0.1936	7,121 0.5969 1.1241 28.9200	13,305 0.1781 0.3079 3.7845	7,086 0.4260 0.2724 1.0000


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11.8Variography

Variograms were calculated for each of the 13 mineralized domains to provide guidance in the selection of search distance and direction for grade estimation. Multiple variograms were run on Au, Ag, sulfide sulfur, and the Cnratau variable.

Figure 11-5 and Figure 11-6 illustrate just a few of the Au and Ag variograms that were completed. Figure 11-5 represents the Au and Ag in the Silicic material between the West Spay and Central Faults (domain 12). Figure 11-6 represents Au and Ag in the Silicic material between the Central Fault and the Footwall of the East Fault (domain 13). These are two of the more important mineralized domains that will contribute to the Mineral Resource.

A scan of the variogram statistics indicates the fewer number of Ag composites compared to the number of gold composites. That contributes to the relative difficultly obtaining clear variograms for silver.


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Figure 11-5: Variograms for Silicic Material Between the West Splay and Central Faults


North–South			East–West


North–South			East–West

Source: Figure prepared by IMC, 2022.


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Figure 11-6: Variograms in Silicic Material Between the Central Fault and the East Fault Footwall


North–South			East–West


North–South			East–West

Source: Figure prepared by IMC, 2022.


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11.9Block Grade Estimation

Block grade estimation was broken into three groups of estimates:

•Au, Ag, and Mercury

•Cnratau

•Sulfide Sulfur

The boundaries and controls on each of the three were different as might be expected with the differences in geologic occurrence in each of the three cases.

The Au and Ag were estimated using the 40 ft composites of the assay database discussed previously. Cnratau utilized the same database and composites but with different boundary controls.

Sulfide sulfur was estimated using a separate composite database of LECO analysis for sulfide sulfur. Those composites were assembled from pulps to provide area coverage of sulfide sulfur data over the economically interesting parts of the project.

The estimation of mercury was added later in response to questions from the project process team and is based on a separate database of ICP analysis that was completed on later drilling.

Inverse distance methods were used for most of the block value estimations. Test runs of ordinary kriging were also completed. The intent of selecting the inverse distance method was to develop a better planning model with less smoothing during block estimation. The intent was to provide an estimate of block values that would be predictive of actual mine head grades once appropriate cutoffs were applied.

11.9.1Gold and Silver

Gold, silver, and mercury utilized the 13 domains defined previously. Those domain boundaries were treated as “hard” boundaries during estimation. All three metals were estimated using the 40 ft composites noted earlier and inverse distance cubed (1/d3) as the estimation method. For Au, the composite values with the factoring removed were used for Au grade estimation. Search parameters are provided on Table 11-7.

Within some domains, a high-grade search limit was applied where composites above a certain grade were not used beyond half of the normal search distance. This process includes the high-grade values but limits their extent to minimize high-grade smearing over neighboring low-grade values.

The grade estimation for all three metals used a maximum of ten composites with a maximum of three composites per drillhole. A single composite could be used to assign a block grade, but that grade would be considered as inferred category (Class is discussed later in this section).


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Table 11-7: Grade Estimation Parameters for Au, Ag, and Mercury


Population Domain Number	Alteration Type and Code	Lithology Type and Code	Structure Block Code	Description	Statistics Summary for 40 ft Composites
					Variable	Orientation, Degrees			Search Radii, ft			Method Inv Dist	HG Limit Grade	HG Limit Search ft
						Dip Dir	Plunge	Rotation	Prim	Second	Perpend
1	Acid Lch 501	All	All	Acid Leach Alteration	Au Ag Mercury	270 270 270	0 0 0	0 0 0	270 270 270	270 270 270	50 50 50	3 3 3	NA NA NA
2	Arg+Prop 502+504	Tsg 4	All	Argillic Lake Sediments	Au Ag Mercury	0 0 0	0 0 0	0 0 0	270 270 270	270 270 270	50 50 50	3 3 3	0.008 NA NA	135
3	Silicic 503	Tsg 4	All	Silicic Lake Sediments	Au Ag Mercury	0 0 0	0 0 0	0 0 0	270 270 270	270 270 270	50 50 50	3 3 3	0.100 NA NA	135
4	Arg+Prop 502+504	All	10	Argillic West of the Range Fault	Au Ag Mercury	270 270 270	0 0 0	0 0 0	150 150 150	150 150 150	50 50 50	3 3 3	0.010 0.300 0.200	75 75 75
5	Arg+Prop 502+504	All	101	Argillic Between Range and West Splay	Au Ag Mercury	270 270 270	0 0 0	0 0 0	300 300 300	300 300 300	50 50 50	3 3 3	NA NA NA
6	Arg+Prop 502+504	All	102	Argillic Between West Splay and Central	Au Ag Mercury	270 270 270	0 0 0	0 0 0	200 200 200	200 200 200	50 50 50	3 3 3	NA NA NA
7	Arg+Prop 502+504	All	203, 204	Argillic Between West Splay and Central South	Au Ag Mercury	270 270 270	0 0 0	0 0 0	250 250 250	250 250 250	50 50 50	3 3 3	0.100 0.600 NA	125 125
8	Arg+Prop 502+504	All	104, 105, 201, 202, 205, 207, 501	Argillic Between Central Fault and East Footwall	Au Ag Mercury	285 285 285	-40 -40 0	0 0 0	300 300 300	300 300 300	50 50 50	3 3 3	0.060 1.500 NA	150 150
9	Silicic 503	All	10	Silicic West of the Range Fault	Au Ag Mercury	270 270 270	0 0 0	0 0 0	200 200 200	200 200 200	50 50 50	3 3 3	0.020 0.800 NA	100 100
10	Silicic 503	All	101	Silicic Between Range and West Splay	Au Ag Mercury	270 270 270	0 0 0	0 0 0	300 300 300	300 300 300	50 50 50	3 3 3	0.029 0.500 NA	150 150
11	Silicic 503	All	102	Silicic Between West Splay and Central	Au Ag Mercury	270 270 270	0 0 0	0 0 0	300 300 300	300 300 300	50 50 50	3 3 3	0.060 0.600 NA	150 150
12	Silicic 503	All	203, 204	Silicic Between West Splay and Central South	Au Ag Mercury	270 270 270	0 0 0	0 0 0	250 250 250	250 250 250	50 50 50	3 3 3	0.020 1.000 NA	125 125
13	Silicic 503	All	104, 105, 201, 202, 205, 207, 501	Silicic Between Central Fault and East Footwall	Au Ag Mercury	285 285 285	-40 -40 0	0 0 0	300 300 300	300 300 300	50 50 50	3 3 3	0.100 2.000 NA	150 150


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11.9.2Cyanide Ratio

About half of the assay database for fire Au was also assayed for cyanide soluble Au. The cyanide soluble assay is a direct indication of the cyanide amenability of the mineralized material to Au and Ag recovery by cyanidation. Much of the upper portion of the deposit received cyanide soluble assays for Au and Ag. To the point that there are more Ag cyanide assays than fire Ag assays.

The Au cyanide assays are the most consistent set of data to estimate the cyanide recovery of the ore. Cnratau was used to indicate cyanide amenability because there are such widely differing numbers of cyanide and fire assay data. The ratio, where it is available, can be interpolated as an indication of oxidation that has occurred in the rock mass.

The domains selected for Au, Ag, and mercury mineralization reflect the original hydrothermal mineralization. The cyanide ratio however reflects the oxidation process as a secondary impact.

A review of cross-sections of the cyanide ratio data indicated two populations of Cnratau:

•A generally horizontal band near topography reflecting surface water and oxidation that looks like a conventional oxidation blanket.

•Isolated values at depth that likely reflect oxidation downward along structure with limited later extent.

In order to estimate Cnratau, a boundary was developed between the upper oxide blanket and the lower structural controlled oxidation. This was completed by visual analysis of Cnratau cross-sections.

The boundary surface was defined as a horizontal plan on the 4000 elevation from the east edge of the model to the 19,000 east line. From there the surface trends upward to the 4400 elevation at the 21,000 east line. From 21,000 east to the east edge of the model the 4400 elevation is applied. Blocks above the surface were coded with a value of 1 in a variable called “Contrat”. Blocks below the surface were coded with a Contrat value of 2.

Table 11 8 summarizes the parameters used to estimate the Cnratau within each block. Once the ratio was assigned, block values of cyanide soluble Au could be calculated where required. Composite requirements: max =10, min =1, max per hole =3.

Table 11-8: Estimation Parameters for Cyanide Ratio


Cn Ratio Domain “Contrast”	Structure Block Code	Description	Statistics Summary for 40 ft Composites
			Variable	Orientation, Degrees			Search Radii, Ft.			Method Inv Dist
				Dip Dir	Plunge	Rotation	Prim	Second	Perpend
1	All	Near Surface Oxidation, East of Central Fault	Cnratau	270	0	0	700	700	50	3
2	104, 105, 201, 202, 205, 207, 501	Structural Oxidation, East of Central Fault	Cnratau	285	-40	0	150	150	50	3
3	10, 101, 102, 201, 202, 203, 204, 205, 206	Structural Oxidation, West of Central Fault	Cnratau	270	0	0	150	150	50	3

11.9.3Sulfide Sulfur

Sulfide sulfur was estimated in order to provide an improved localized cost for concentrate processing. The cost of concentrate processing is dependent on the amount of sulfide sulfur in the mill feed. Most of the sulfide sulfur is in the form of pyrite. Pyrite exists everywhere throughout the deposit, including in the oxidized portion. In particular, the acid leach alteration type also contains native sulfur which also reports to the LECO assay method for sulfide sulfur. The acid leach alteration was broken out separately for estimation and is not planned for processing.

The presence of sulfide sulfur is not impacted by the oxidation state or rock type. Population tests indicate that the only independent population is the acid leach alteration. The dip orientation for the estimation parameters were however adjusted based on structure.

The sulfide sulfur LECO data was performed on selected drillholes. Physical composites 25 ft long were assembled for submittal to LECO analysis by Hycroft. Once a hole was selected, the 25 ft downhole composites were continuous for the


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length of the hole. These composites were used for input for block estimation without further compositing. The holes selected for LECO analysis generally target the Vortex pit area with roughly 400 ft spacings between them.

Table 11-9 summarizes the estimation parameters used to assign sulfide sulfur to the model blocks.

Table 11-9: Sulfide Sulfur Estimation Parameters


Alteration Type “hyc_alt”	Structure Block Code	Description	Statistics Summary for 40 ft Composites
			Variable	Orientation, Degrees			Search Radii, Ft			Method Inv Dist
				Dip Dir	Plunge	Rotation	Prim	Second	Perpend
501	All	Acid Leach Alteration	Sulfd	270	0	0	650	650	200	3
All but 501	104, 105, 201, 202, 205, 207, 501	Lith and laceration East of Central Fault	Sulfd	285	-40	0	650	650	200	3
All but 501	10, 101, 102, 201, 202, 203, 204, 205, 206	Lith and Laceration West of Central Fault	Sulfd	270	0	0	650	650	200	3

Due to the few number of sulfide sulfur composites, default values were assigned based on alteration type to those blocks without estimated sulfide sulfur. Sulfide sulfur is an input to project cost so leaving blocks unestimated would underestimate project costs.

The default values were assigned as follows in Table 11-10. Default values were assigned to blocks that were estimated for Au or Ag and did not receive a sulfide sulfur value from the estimation process noted on Table 11-10.

Table 11-10: Sulfide Sulfur Default Values if Not Estimated


Alteration Type “hyc_alt”	Description	Default Sulfide Sulfur %
501	Acid Leach	1.8972
502	Argillic	1.6092
503	Silicic	1.8762
504	Propylitic	1.6090
0 or 505	Unassigned	1.7477

Defaults used if Not Estimated

Defaults Assigned if Au or Ag >0

11.9.4Density

Bulk density was assigned to in-situ rock based on density data collected by Hycroft and their predecessors. Average density values were set based on alteration type within the hard or in-situ units. The exception was the ALS rock type which was assigned a single value not impacted by alteration.

Alluvium, back fill, and stockpiles were guided by the few test values available but were generally based on the density values assigned to the previous block model completed in 2019. There is a slight increase in the density of sulfide stockpiles compared to general back fill or dump stockpiles.

Table 11-11 summarizes the densities assigned to the model.


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Table 11-11: Density Assigned to the Block Model


Alteration Type “hyp_alt”	Lithology Code “hyc_geol”	Description	Specific Gravity	Lbs/Cu ft	Ktons per Model Block
501	All	Acid Leach	2.2654	141.36	4.524
502	All	Argillic	2.2094	137.87	4.412
503	All	Silicic	2.5055	156.34	5.033
504	All	Propylitic	2.3193	144.72	4.631
	2	Alluvium	1.7808	111.12	3.556
	7	Auld Lang Syne	2.6520	165.48	5.296

Stockpile “stkptyp”			Specific Gravity	Lbs/Cu ft	Ktons per Block
802 80108 80109 80110 80100, NW+Geb Fill Sulfide Stkps 80101 80102 80103 80104 + 80105 80106 80107, Central+Brim Stkps 80120, Crofoot Leach Pad			1.6026	100.00	3.2000
			1.7049	106.39	3.4040
			2.0000	124.80	3.9936

11.9.5Stockpile Grade Estimation

The Hycroft pits have incurred both backfilling and in-pit stockpiling. In particular, potential sulfide mill feed that has been incurred during the mining of oxide heap leach ores have been stockpiled. That material is potential future mill feed to a sulfide processing facility.

Hycroft provided interpreted solids based on survey of many of the stockpiles. Where possible they provided the average tonnage and grade of each stockpile based on their mineralized material control information when the material was mined. In addition, there were a number of additional in-pit fill areas that were modeled within the previous 2019 model. Most of those were in the north area of the project in the old Bay pit.

IMC utilized the Hycroft solids to code model blocks as stockpile or fill. Where the 2019 model had backfill codes, IMC utilized those codes in an effort to account for all in-pit materials. In addition, the Crofoot leach pad is located west of the Central Pit area. That material has been coded in order to prevent assignment of grade from original in-situ assay samples.

Some of the stockpiles at Hycroft have been drilled by Sonic drilling and sampling methods. The grade of those stockpiles that contained sonic drilling was assigned with the sonic assays. Where there were no sonic assays in a stockpile block, the mineralized material control grades provided by Hycroft were assigned to the stockpile blocks. Densities were assigned as summarized in the previous sub-section.

Blocks were assigned stockpile codes as summarized on Table 11-12.


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Table 11-12: Stockpile Grade Estimation of Assignments


Stockpile Codes	Location	Variables Estimated
		Au, Ag, Sulfide Sulfur, CnAu/FaAu Ratio
80100	Brim Pit
80101	Brim Pit	Search Distances			Estimation Method
80102	Crusher Stockpile	North ft	East ft	Vert ft
80104	Central Pit	600	600	200	1/D1
80120	Crofoot Pad

Stockpile Grades Assigned by Hycroft Production History
Stockpile Codes	Location	Au oz/ton	Ag oz/ton	Sulfide Sulfur %	CnAu/FaAu Ratio
80103	Central Pit	0.0131	0.2308	1.89	0.25
80105	Central Pit	0.0148	0.6514	2.51	0.20
802	General Fill	0.0000	0.0000	0.00	0.00
80108	NW Area	0.0000	0.0000	0.00	0.00
80109	NW Area	0.0000	0.0000	0.00	0.00
80110	NW Area	0.0000	0.0000	0.00	0.00

The Crofoot leach pad (code 80120) was assigned a confidence class. All other stockpiles with grade were assigned a confidence class for indicated.

11.10Classification

Individual blocks in the model were assigned classification codes as defined within NI 43-101 and the CIM best practices. As noted earlier the stockpiles were assigned classification codes of 2 for Indicated class and the Crofoot stockpile was assigned a code of 3 for inferred.

The in-situ rock values were assigned classification codes based on the inverse distance estimation of Au. During that estimation process, the number of composites that were used to estimate the block was stored along with the distance between the block and the closest composite. Those two parameters were used to assign classification code in the following manner.

If closest distance <= 125 ft and number of composites = 10, Class=1 Measured

Else if

If closest distance <=225 ft and number of composites >=4,

and Ag was estimated, then Class=2 Indicated

Otherwise

Remaining Blocks Class=3, Inferred

The process was actually completed in reverse order to that summarized above so that indicated overprinted inferred and both were overprinted by measured where required. There are some blocks that may have met the criteria for indicated classification based on the estimation of gold that were moved to inferred class because there was no silver estimate. Additional silver data to allow for the estimation of more silver blocks could benefit the project by moving some of this material to the indicated classification.

11.11Model Verification

The block model was verified by several methods before being used to determine mineral resources.

•Detailed Visual Checks of Drilling versus Block Estimates;

•Swath Plots;


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•IMC Smear Check;

•Reconciliation to Production History;

The visual check of the block model was one of the most useful and informative processes that was used to confirm the practicality of the block model. IMC completed visual checks on plan and section for all of the estimated variables in the model. In addition to IMC visual checks, the Hycroft engineering and geology team on site also reviewed the model and helped IMC identify and correct coding issues prior to finalizing the block model.

11.11.1Swath Plots

Swath plots are a practice now common among resource modelers to provide a visual indication if the block model follows the grade trends indicated by the supporting data and if there is any observable local bias in the block grade estimation.

Figure 11-7 illustrates the average grades of contained composites and block model grades for horizontal slices through the block model for Au and Ag. The Ag model has smoothed out the composite grade distribution and indicates a model low bias of Ag. This is due to the few number of Ag composites (roughly 30% of the number of Au composites). Searching to fill the blocks with Ag grade has resulted in an overly smoothed result. Had there been more Ag assay and composites, the Ag model would more closely track the composite grade variation.

Figure 11-8 illustrates the composite and block grade comparison for vertical slices in the east–west orientation. The smoothing issue of Ag is also present on the vertical sections.

In both plots, only in-situ block grades are being compared to non-sonic drill composites. Stockpiles have been removed from the swath plots.


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Figure 11-7: Vertical Swath Plots for Gold and Silver

Source: Figure prepared by IMC, 2022.


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Figure 11-8: Vertical Swath Plots for Gold and Silver

Source: Figure prepared by IMC, 2022.


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11.11.2Smear Check

IMC uses a simple test to understand the amount of grade smoothing within the block model and to confirm that the model grades are not high biased. The test is referred to internally as the “smear check.”

The procedure is as follows:

•A range of cutoff grades are selected for the check process. Typically, they bracket the potential planning cutoff grades.

•For each cutoff grade being tested, the blocks above cutoff are identified.

•All composites contained within those blocks are identified.

•The average grade of the composites and blocks are tabulated.

•The percentage of the contained composites less than cutoff are calculated.

Table 11-13 summarizes the results for both Au and Ag in-situ rock. Stockpiles and sonic drillholes have been removed from this analysis.

Table 11-13: IMC Smear Check


Au Composites vs Model Au 1/D3
Cutoff Grade	% Comps Less than Cutoff	Number of Comps In Shape	Composite Grade oz/ton	Number of Blocks in Shape	Model Grade oz/ton
0.002	7.99	35,969	0.010	819,615	0.008
0.003	8.10	33,339	0.010	738,740	0.009
0.004	9.97	31,018	0.011	667,422	0.009
0.005	12.35	28,591	0.012	593,553	0.010
0.006	15.26	25,796	0.012	518,085	0.011
0.007	17.26	22,927	0.013	442,113	0.011
0.008	19.55	19,974	0.014	369,140	0.012
0.009	20.23	17,078	0.015	304,207	0.013
0.010	21.41	14,514	0.016	248,062	0.014

Ag Composites vs Model Ag 1/D3
Cutoff Grade	% Comps Less than Cutoff	Number of Comps In Shape	Composite Grade oz/ton	Number of Blocks in Shape	Model Grade oz/ton
0.100	2.39	10,259	0.558	510,279	0.402
0.200	6.97	8,674	0.628	409,373	0.460
0.300	12.96	5,447	0.851	226,124	0.634
0.400	15.40	3,805	1.069	140,759	0.810
0.500	15.42	2,795	1.293	95,009	0.986
0.600	16.67	2,195	1.499	65,868	1.180
0.700	17.10	1,754	1.709	49,036	1.364
0.800	16.64	1,454	1.908	37,854	1.547
0.900	17.09	1,235	2.095	29,645	1.740
1.000	17.60	1,051	2.299	23,249	1.958

The test results are positive. In all cases the model grade is properly less than the grade of the contained composites because the model block grade estimation utilized composite data that was located outside of the shape being tested. If the model grade were higher than the grade of the contained composites, there would be indication of high bias within the model.


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The percentage of composites less than the tested cutoff is generally small in the range of applicable cutoff grades. Percentages in the range of 15% are typical for well zoned deposits. Values less than 10% in the range of cutoff grades for Au indicate that the model has done a reasonable job of following the local data. The higher percentage levels in the high-grade ranges are typical of the smoothing process that result in any grade estimator.

11.11.3Reconciliation

IMC completed a reconciliation of the model against 19 months of reported production for all of 2020 and 2021 up through the end of July. The reported 2019 production from Hycroft included substantial stockpile reclaim that would not be indicative of the block model response. The 19-month time period for the test is relatively short with a total of 13,584 ktons of oxide ore delivered to the leach pad. This represents about 65% of processing the sulfide mineralized materials for 1 year.

During 2020, Hycroft delivered ROM to the leach pad and crush leach to the crusher prior loading on the pad. Sulfide material that was being considered for a sulfide atmospheric leach was stockpiled for future processing. Hycroft provided IMC with calculations for materials control routing that are used at site. Those methods were set up for application to the 2021 block model by IMC.

Some modifications were made by IMC during the installation of the materials control procedure. During 2021, Hycroft stopped crushing leached oxide ore and shipped ROM oxide ore only to the pad. IMC assumed that material that would report to crush leach would instead be shipped directly as ROM to the pad.

Hycroft provided surface files that reflect the mine survey progress. The surface files were used to measure the material within the block model for each of the time periods at the cutoffs reportedly applied during the control.

Table 11-14 summarizes the results of the model estimate of processed sulfide materials plus leached oxide ore versus production reported from materials control. Tonnage from the model is about 4% less than reported by the materials control. Gold grade is substantially lower than the materials control grade from blast holes.

A check of the database composites contained within the materials control shapes indicate that average of the composites contained in the materials control are less than the materials control grade and match the predicted grade from the block model. As a result, the composite data could not generate a gold grade as high as that reported by materials control. The difference may be due to smaller selective mining units or blast hole bias. In summary, the data within the mining shapes could not support grades that are different from those estimated in the model.


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Table 11-14: Reconciliation Summary, 19 Months of Production Versus the Block Model Reporting of the Same Volume


Block Model Estimate of Production
Year	Material Type	Ktons	Fa Au oz/ton	Fa Ag oz/ton		Sulfide Sulfur %	Waste ktons	Total Ktons
2020	Sulfide Leach Total	4,308 1,168 5,476	0.009 0.010 0.009	0.34 0.37 0.35		2.33 1.87 2.23	5,710	11,186
Jan-Jul 2021	Sulfide Leach Total	522 7,038 7,560	0.008 0.010 0.010	0.25 0.51 0.50		2.24 2.10 2.11	3,761	11,321
2020 – Jul 2021	Sulfide Leach Total	4,830 8,206 13,036	0.009 0.010 0.010	0.33 0.49 0.43		2.32 2.07 2.16	9,471	22,507
Model Compared to the Control
		-4.0%	-31.6%	55.8%		20.3%	17.5%	4.0%
Mean of Data Base Composites in the Control Geometries Above Cutoff
			0.010	0.43

Control Production Report
Year	Material Type	Ktons	Fa Au oz/ton	Fa Ag oz/ton	Sulfide Sulfur %		Waste ktons	Total Ktons
2020	Sulfide Leach Total	4,145 2,669 6,814	0.014 0.0151 0.014	0.209 0.2979 0.24	1.99 1.6753 1.87		4,372	11,186
Jan-Jul 2021	Sulfide Leach Total	1,093 5,677 6,770	0.013 0.014 0.014	0.334 0.307 0.31	2.07 1.66 1.73		3,686	10,456
2020-Jul 2021	Sulfide Leach Total	5,238 8,346 13,584	0.014 0.014 0.014	0.24 0.30 0.28	2.01 1.66 1.80		8,058	21,642

11.12Mineral Resources

Mineral resources were developed using the block model and pit optimization software to determine the mineralization with reasonable expectation of economic extraction as defined by NI 43-101 and CIM best practices.

Table 11-15 summarizes the economic parameters that were used to define the optimized pit that defined the Mineral Resource. Metal prices for Mineral Resource were US$1,800/oz Au and US$23.00/oz Ag.

Each block is evaluated to determine which process provides the best net return after operating cost. The two processes are:

•ROM cyanide heap leaching, or

•Flotation milling followed by POX.

Both process material types are reported on the statement of mineral resources.

Table 11-16 summarizes the mineral resource. The risks to the Mineral Resource are project costs and project recoveries as well as metal prices that can have a substantial impact on the Mineral Resource both positively and negatively.

Mineral resources are not mineral reserves and detailed economic considerations have not been applied. Modifying factors for mine and process design have not been applied.

The Mineral Resource on Table 11-16 represents the total amount of material in the ground that meets the requirements for Mineral Resource.


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Table 11-15: Economic Parameters for Mineral Resources


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Table 11-16: Hycroft Mineral Resources as of February 18, 2022


Classification	Cutoff Grade $ Net of Process	Approximate Cutoff, AuEq Au oz/ton	Ktons	Au oz/ton	Ag oz/ton	Sulfide Sulfur%	Au Contained Ounces (000)	Ag Contained Ounces (000)
Heap Leach Resource
Measured	$0.01	0.003	97,086	0.008	0.30	2.75	777	29,417
Indicated	$0.01	0.003	36,046	0.007	0.29	2.10	252	10,417
Meas + Ind	$0.01	0.003	133,132	0.008	0.30	2.57	1,029	39,834
Inferred	$0.01	0.003	101,314	0.008	0.09	1.77	811	9,118

Mill, Flotation Concentrate, POX and Cyanide Leach Process Plant
Measured	$0.01	0.011	372,226	0.013	0.65	1.86	4,839	240,830
Indicated	$0.01	0.011	314,866	0.012	0.53	1.65	3,778	165,305
Meas + Ind	$0.01	0.011	687,092	0.013	0.59	1.76	8,617	406,135
Inferred	$0.01	0.011	349,659	0.012	0.40	1.19	4,196	141,262

Combined Mineral Resources Leach Plus Process Plant
Measured	$0.01	0.003 - 0.011	469,312	0.012	0.58	2.04	5,616	270,247
Indicated	$0.01	0.003 - 0.011	350,912	0.011	0.50	1.70	4,030	175,722
Meas + Ind	$0.01	0.003 - 0.011	820,224	0.012	0.54	1.90	9,646	445,969
Inferred	$0.01	0.003 - 0.011	450,973	0.011	0.33	1.32	5,007	150,380

Notes:

Mineral resources based on metal prices of $1,800/troy oz Au and $23.00/troy oz Ag

Cutoffs are income – process cost = NPR = NSR – Process Opex

Numbers may not match exactly due to rounding.

Mineral resources are contained within a computer-generated optimized pit. Total material in that pit is 3.516 billion tons

All units are imperial. Ktons means 1,000 short tons of 2,000 lbs. Au and Ag grades are in troy ounces/short ton.


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12MINERAL RESERVE ESTIMATES