8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): January 8, 2026

Core Natural Resources, Inc.

(Exact name of registrant as specified in its charter)

275 Technology Drive Suite 101

Canonsburg, Pennsylvania 15317

(Address of principal executive offices)

(Zip code)

Registrant's telephone number, including area code:

(724) 416-8300

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.04 Mine Safety – Reporting of Shutdowns and Patterns of Violations.

On January 8, 2026, Mingo Logan Coal LLC, a subsidiary of Core Natural Resources, Inc., received an imminent danger order under section 107(a) of the Federal Mine Safety and Health Act of 1977 at the Mountaineer II mine located in Logan County, West Virginia. The order states that an inspector found an accumulation of elevated methane levels in an isolated section of the mine. Mine personnel promptly took appropriate actions to alleviate the condition and restored acceptable methane levels. The Mine Safety and Health Administration has terminated the 107(a) order, and no injuries or illnesses resulted from the temporary condition.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: January 12, 2026