Note 3 - Property, Plant and Equipment (Tables)

9 Months Ended

Sep. 30, 2020

Property, Plant and Equipment [Abstract]

Schedule of property, plant, and equipment

(In thousands)	September 30, 2020		December 31, 2019
Plant and equipment	$	154,655	$	142,773
Construction in process		6,882		11,986
Capitalized mine development costs		70,413		58,773
Less: accumulated depreciation and amortization		(50,931)		(35,330)
Total property, plant and equipment, net	$	181,019	$	178,202

Schedule of depreciation and amortization

	Three months ended September 30,				Nine months ended September 30,
(In thousands)	2020		2019		2020		2019
Depreciation of plant and equipment	$	4,326	$	3,706	$	12,740	$	10,142
Amortization of capitalized
mine development costs		932		1,647		2,861		4,149
Total depreciation and amortization	$	5,258	$	5,353	$	15,601	$	14,291