Note 3 - Property, Plant and Equipment - Depreciation and amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Property, plant, and equipment
Depreciation of plant and equipment	$ 37,283	$ 30,913	$ 24,132
Amortization of right of use assets (finance leases)	10,414	8,547	4,846
Amortization and depletion of capitalized mine development costs and mineral rights	17,918	14,792	12,216
Total depreciation, depletion, and amortization	65,615	$ 54,252	$ 41,194
Knox Creek preparation plant
Property, plant, and equipment
Total depreciation, depletion, and amortization	$ 1,100