Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Plant, Equipment, and Mine Development, Net - Components of plant, equipment, and mine development, net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Feb. 28, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Plant, equipment and mine development, gross	$ 92,489		$ 85,256
Less, accumulated depreciation and amortization	(26,134)		(25,033)
Total	66,355		60,223
Leach pads
Property, Plant and Equipment [Line Items]
Plant, equipment and mine development, gross	17,432		17,432
Process equipment
Property, Plant and Equipment [Line Items]
Plant, equipment and mine development, gross	$ 17,459		16,065
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Useful life	10 years
Plant, equipment and mine development, gross	$ 10,507		10,507
Mine equipment
Property, Plant and Equipment [Line Items]
Plant, equipment and mine development, gross	6,707		5,961
Vehicles
Property, Plant and Equipment [Line Items]
Plant, equipment and mine development, gross	$ 1,227		991
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Useful life	7 years
Plant, equipment and mine development, gross	$ 341		322
Mine development
Property, Plant and Equipment [Line Items]
Plant, equipment and mine development, gross	1,096		756
Mineral properties
Property, Plant and Equipment [Line Items]
Plant, equipment and mine development, gross	37		37
Construction in progress and other
Property, Plant and Equipment [Line Items]
Plant, equipment and mine development, gross	$ 37,683	$ 34,100	$ 33,185
Minimum \| Process equipment
Property, Plant and Equipment [Line Items]
Useful life	5 years
Minimum \| Mine equipment
Property, Plant and Equipment [Line Items]
Useful life	5 years
Minimum \| Vehicles
Property, Plant and Equipment [Line Items]
Useful life	3 years
Maximum \| Process equipment
Property, Plant and Equipment [Line Items]
Useful life	15 years
Maximum \| Mine equipment
Property, Plant and Equipment [Line Items]
Useful life	7 years
Maximum \| Vehicles
Property, Plant and Equipment [Line Items]
Useful life	5 years