Property, Plant and Mine Development, net - Summary of Property, Equipment and Mine Development (Details) - USD ($) $ in Thousands		Jun. 30, 2022	Dec. 31, 2021
Property, equipment and mine development - net
Property and equipment, gross	[1]	$ 271,665	$ 261,938
Accumulated depreciation and amortization		(118,888)	(105,167)
Total property, equipment and mine development - net		152,777	156,771
Accrued capital expenditures		100	1,700
Asset retirement costs
Property, equipment and mine development - net
Property and equipment, gross		1,065	1,065
Construction-In-Progress
Property, equipment and mine development - net
Property and equipment, gross		2,729	15,854
Furniture and office equipment
Property, equipment and mine development - net
Property and equipment, gross		1,703	1,685
Land
Property, equipment and mine development - net
Property and equipment, gross		9,230	9,230
Mineral interests
Property, equipment and mine development - net
Property and equipment, gross		79,543	79,964
Light Vehicles And Other Mobile Equipment
Property, equipment and mine development - net
Property and equipment, gross		2,376	2,224
Machinery And Equipment
Property, equipment and mine development - net
Property and equipment, gross		39,288	33,213
Mill facilities and infrastructure
Property, equipment and mine development - net
Property and equipment, gross		35,200	24,973
Mine Development
Property, equipment and mine development - net
Property and equipment, gross		98,900	92,138
Software and licenses
Property, equipment and mine development - net
Property and equipment, gross		$ 1,631	$ 1,592

[1] Includes accrued capital expenditures of $0.1 million and $1.7 million at June 30, 2022 and December 31, 2021, respectively.