5.FAIR VALUE MEASUREMENTS

The following table summarizes certain fair value measurements within the hierarchy not included elsewhere in these notes:

Fair Value

 

Carrying
Value

  ​ ​ ​

Level 1

  ​ ​ ​

Level 2

  ​ ​ ​

Level 3

  ​ ​ ​

(in thousands)

December 31, 2025

Recorded on a recurring basis:

Digital assets

$

51,834

$

51,834

$

$

Contingent consideration

$

18,000

$

$

$

18,000

Additional disclosures:

Long-term debt

$

463,456

$

$

508,844

$

December 31, 2024

Recorded on a recurring basis:

Digital assets

$

45,037

$

45,037

$

$

Contingent consideration

$

13,100

$

$

$

13,100

Additional disclosures:

Long-term debt

$

490,387

$

$

523,461

$

The carrying amounts for cash equivalents, accounts receivable, accounts payable, accrued and other liabilities, approximate fair value due to the short maturity of those instruments.

The fair value of our digital assets is based on an exchange quoted price. See Note 7 – Digital Assets for more information on our digital assets.

The fair value measurement of our contingent consideration liability is determined using an option approach methodology simulation based on significant inputs not observable in active markets representing a Level 3 fair value measurement under the fair value hierarchy. Our contingent consideration liability is associated with our acquisition of our Hamilton County Coal, LLC (“Hamilton”) mine in 2015 wherein we agreed to pay the seller additional consideration for the acquisition if the average quarterly sales price exceeds a defined threshold price in any future quarter subject to a maximum of $110.0 million reduced for any payments made under an overriding royalty agreement with the sellers relating to mineral interests controlled by our Hamilton mine. We have paid $16.1 million under this contingent consideration agreement and $0.7 million under the overriding royalty agreement as of December 31, 2025.

The estimated fair value of our long-term debt, including current maturities, is based on interest rates that we believe are currently available to us in active markets for issuance of debt with similar terms and remaining maturities. See Note 12 – Long-Term Debt for additional information on our long-term debt.

Quantitative Information about Level 3 Fair Value Measurements

Contingent Consideration

Our option approach methodology simulation generates an expected payment for each quarter in Hamilton’s expected mine life by using proprietary internal estimates of our uncommitted coal sales prices and generating a simulated uncommitted coal sales price by applying unobservable inputs through a million simulations. This simulated coal sales price is then used in a calculation of the expected future payments using our proprietary committed coal sales prices and production for each quarter. We then calculate the present value of the estimated future payments. The following table presents quantitative information about certain significant unobservable inputs used in the fair value measurement for our contingent consideration liability. The use of significant unobservable inputs results in uncertainty as of the reporting date, as changes in these unobservable inputs could significantly raise or lower the estimated fair value.

 

Valuation Technique(s)

 

Unobservable Input

 

Range/Amount
(Average) (a)

December 31, 2025

Contingent Consideration

Option approach methodology simulation

Cost of Debt

5.46% - 8.35%

Coal price volatility

9.2%

Market price of risk adjustment (annual)

6.7%

December 31, 2024

Contingent Consideration

Option approach methodology simulation

Cost of Debt

6.51% - 8.56%

Coal price volatility

6.2%

Market price of risk adjustment (annual)

6.2%

(a)Averages represent the arithmetic average of the inputs and is not weighted by a relative fair value or notional amount.

The following table represents changes in our contingent consideration liability:

Year Ended December 31, 

  ​ ​ ​

2025

2024

 

(in thousands)

Beginning balance

$

13,100

$

9,900

Noncash changes in fair value (1)

11,340

10,989

Payments

(6,440)

(7,789)

Ending balance

$

18,000

$

13,100

(1)Noncash changes in the fair value of our continent consideration liability are included in the Operating expenses (excluding depreciation, depletion and amortization) line item within our consolidated statements of income.

Historical Timeline

Fiscal YearFiled
2025Feb 26, 2026Showing above
2024Feb 27, 2025
2023Feb 23, 2024
2022Feb 24, 2023
2021Feb 25, 2022
2020Feb 23, 2021
2019Feb 20, 2020
2018Feb 22, 2019
2017Feb 23, 2018
2016Feb 24, 2017
2015Feb 26, 2016

About Fair Value Disclosures

Fair value disclosures classify all assets and liabilities measured at fair value into a three-level hierarchy: Level 1 (quoted market prices), Level 2 (observable inputs like yield curves), and Level 3 (unobservable inputs requiring management estimates). The proportion of Level 3 assets directly reflects how much of the balance sheet depends on internal models rather than market evidence.

Key signals: a growing Level 3 balance relative to total fair-value assets increases valuation uncertainty and earnings volatility risk. Watch for transfers between levels — assets moving from Level 2 to Level 3 often signal deteriorating market liquidity. Unrealized gains and losses on Level 3 positions flow through earnings or other comprehensive income, so large swings deserve scrutiny. For financial institutions, examine the sensitivity disclosures that show how Level 3 valuations change under alternative assumptions. Compare the fair value of debt against its carrying amount to gauge hidden leverage.