Business and Basis of Presentation (Policies)	6 Months Ended
Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation Together, the condensed consolidated statements of operations, comprehensive loss, balance sheets, cash flows and stockholders’ equity for the Company are referred to as the “Condensed Consolidated Financial Statements.” The Condensed Consolidated Financial Statements are also referenced across periods as “Condensed Consolidated Statements of Operations,” “Condensed Consolidated Statements of Comprehensive Loss,” “Condensed Consolidated Balance Sheets,” “Condensed Consolidated Statements of Cash Flows,” and “Condensed Consolidated Statements of Stockholders’ Equity.” The Condensed Consolidated Financial Statements include all wholly-owned subsidiaries’ results of operations for the three and six months ended June 30, 2026 and 2025. All significant intercompany transactions and balances have been eliminated in consolidation. The accompanying interim Condensed Consolidated Financial Statements are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) and in accordance with the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for Form 10-Q. Such rules and regulations allow the omission of certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. GAAP as long as the financial statements are not misleading. In the opinion of management, these interim Condensed Consolidated Financial Statements reflect all normal and recurring adjustments necessary for a fair presentation of the results for the periods presented. Results of operations for the three and six months ended June 30, 2026 are not necessarily indicative of the results to be expected for the year ending December 31, 2026 or any other period. These interim Condensed Consolidated Financial Statements should be read in conjunction with the Company’s Consolidated Financial Statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025.
Reclassifications	Reclassifications Certain amounts in the prior year Condensed Consolidated Statements of Cash Flows have been reclassified to conform to the current year presentation.
Asset Impairment	Asset Impairment As of March 31, 2026, due to declines in pricing forecasts for U.S. High-Vol. metallurgical coal products, the Aracoma and Kingston/Mammoth mining complexes were tested for impairment. Estimated future undiscounted cash flows were projected to exceed each complex’s respective carrying value and no impairment charges were required.
Government Grants	Government Grants The Company recognizes government grants related to income when compliance with grant terms and receipt are considered probable. Grants are recognized in income over the periods in which the Company recognizes as expenses the costs for which the grant was intended to compensate. Grant income is recorded as a reduction to the related expense amounts. On July 4, 2025, legislation commonly referred to as the “One Big Beautiful Bill Act” (“OBBBA”) was signed into law. As part of the OBBBA, metallurgical coal was added to the list of “applicable critical minerals” making the Company eligible for the Internal Revenue Code (“IRC”) Section 45X tax credit (also known as the advanced manufacturing production credit). The IRC Section 45X tax credit will generally provide the Company with a refundable tax credit equal to 2.5% of production costs for metallurgical coal produced and sold in tax years 2026 through 2029. As the IRC Section 45X tax credit is refundable, the Company accounts for the tax credit as a government grant.
Recent Accounting Guidance	Recent Accounting Guidance Refer to the “Recent Accounting Guidance Issued Not Yet Effective” section of Note 2 to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025.

Business and Basis of Presentation (Policies)

6 Months Ended

Jun. 30, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Together, the condensed consolidated statements of operations, comprehensive loss, balance sheets, cash flows and stockholders’ equity for the Company are referred to as the “Condensed Consolidated Financial Statements.” The Condensed Consolidated Financial Statements are also referenced across periods as “Condensed Consolidated Statements of Operations,” “Condensed Consolidated Statements of Comprehensive Loss,” “Condensed Consolidated Balance Sheets,” “Condensed Consolidated Statements of Cash Flows,” and “Condensed Consolidated Statements of Stockholders’ Equity.”

The Condensed Consolidated Financial Statements include all wholly-owned subsidiaries’ results of operations for the three and six months ended June 30, 2026 and 2025. All significant intercompany transactions and balances have been eliminated in consolidation.

The accompanying interim Condensed Consolidated Financial Statements are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) and in accordance with the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for Form 10-Q. Such rules and regulations allow the omission of certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. GAAP as long as the financial statements are not misleading. In the opinion of management, these interim Condensed Consolidated Financial Statements reflect all normal and recurring adjustments necessary for a fair presentation of the results for the periods presented. Results of operations for the three and six months ended June 30, 2026 are not necessarily indicative of the results to be expected for the year ending December 31, 2026 or any other period. These interim Condensed Consolidated Financial Statements should be read in conjunction with the Company’s Consolidated Financial Statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025.

Reclassifications

Certain amounts in the prior year Condensed Consolidated Statements of Cash Flows have been reclassified to conform to the current year presentation.

Asset Impairment

As of March 31, 2026, due to declines in pricing forecasts for U.S. High-Vol. metallurgical coal products, the Aracoma and Kingston/Mammoth mining complexes were tested for impairment. Estimated future undiscounted cash flows were projected to exceed each complex’s respective carrying value and no impairment charges were required.

Government Grants

The Company recognizes government grants related to income when compliance with grant terms and receipt are considered probable. Grants are recognized in income over the periods in which the Company recognizes as expenses the costs for which the grant was intended to compensate. Grant income is recorded as a reduction to the related expense amounts.

On July 4, 2025, legislation commonly referred to as the “One Big Beautiful Bill Act” (“OBBBA”) was signed into law. As part of the OBBBA, metallurgical coal was added to the list of “applicable critical minerals” making the Company eligible for the Internal Revenue Code (“IRC”) Section 45X tax credit (also known as the advanced manufacturing production credit). The IRC Section 45X tax credit will generally provide the Company with a refundable tax credit equal to 2.5% of production costs for metallurgical coal produced and sold in tax years 2026 through 2029. As the IRC Section 45X tax credit is refundable, the

Company accounts for the tax credit as a government grant.

Recent Accounting Guidance

Refer to the “Recent Accounting Guidance Issued Not Yet Effective” section of Note 2 to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025.