Core Natural Resources, Inc. Reports Material Event

Core Natural Resources, Inc. disclosed that it has resumed longwall operations at its Leer South mine in West Virginia and provided an update on productivity levels at its West Elk mine in Colorado.

Accepted by SEC EDGAR 12/18/2025 - 07:08 AM EST Learn about SEC filing dates

Rhea-AI Filing Summary

Core Natural Resources, Inc. disclosed that it has resumed longwall operations at its Leer South mine in West Virginia and provided an update on productivity levels at its West Elk mine in Colorado. This information is contained in a press release dated December 18, 2025, which is furnished as Exhibit 99.1 under Regulation FD and is not deemed filed under Section 18 of the Exchange Act or Sections 11 and 12(a)(2) of the Securities Act.

Insights

Equity and operations analyst

Core describes a Leer South restart and West Elk productivity update.

Core Natural Resources furnished a Regulation FD disclosure noting the restart of longwall operations at its Leer South mine in West Virginia and an update on productivity at its West Elk mine in Colorado. The operational details are provided in a press release dated December 18, 2025 that is attached as Exhibit 99.1.

The company designates this information as furnished rather than filed, so it is not subject to certain liability provisions under the Exchange Act and Securities Act. The emphasis is on mine operating status and productivity, with no specific production or financial figures included in the excerpt.

8-K Event Classification

2 items: 7.01, 9.01

2 items

Item 7.01 Regulation FD Disclosure Disclosure

Material non-public information disclosed under Regulation Fair Disclosure, often investor presentations or guidance.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, or exhibit attachments filed with this report.

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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): December 18, 2025

Core Natural Resources, Inc.

(Exact name of registrant as specified in its charter)

Delaware

001-38147

82-1954058

(State or other jurisdiction of incorporation)

(Commission File Number)

(IRS Employer Identification No.)

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

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

Title of each class			Trading Symbol(s)			Name of each exchange on which registered
Common Stock, $0.01 par value			CNR			New York Stock Exchange

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))

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 7.01 Regulation FD Disclosure.

On December 18, 2025, Core Natural Resources, Inc. (the “Company”) issued a press release announcing that the Company has resumed longwall operations at its Leer South mine in West Virginia and providing an update regarding the productivity levels of its West Elk mine in Colorado. A copy of the press release is furnished as Exhibit 99.1 hereto and is incorporated herein by reference.

The information contained in this Item 7.01 and Exhibit 99.1 shall be considered “furnished” and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that Section or Sections 11 and 12(a)(2) of the Securities Act of 1933, as amended, nor shall it be deemed incorporated by reference into any reports or filings with the Securities and Exchange Commission, whether made before or after the date hereof, except as expressly set forth by specific reference in such a filing.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit 99.1        Press release of Core Natural Resources, Inc. dated December 18, 2025

Exhibit 104        Cover Page Interactive Data File (formatted as inline XBRL and contained in Exhibit 101)

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.

			Core Natural Resources, Inc.
			(Registrant)
			By:			/s/ MITESHKUMAR B. THAKKAR
						Miteshkumar B. Thakkar
						Chief Financial Officer and President

Dated: December 18, 2025