Note 3 - Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment.

Schedule of property, plant, and equipment

	December 31,
(In thousands)	2021		2020
Plant and equipment	$	167,019	$	155,173
Mining property and mineral rights		26,064		76
Construction in process		9,972		7,245
Capitalized mine development costs		104,291		74,279
Less: accumulated depreciation and amortization		(80,269)		(56,242)
Total property, plant and equipment, net	$	227,077	$	180,531

Schedule of depreciation and amortization

	Year ended December 31,
(In thousands)	2021		2020		2019
Depreciation of plant and equipment	$	17,945	$	17,094	$	14,219
Depreciation of right of use assets		1,109		—		—
Amortization of capitalized
mine development costs		7,151		3,818		5,302
Total depreciation and amortization	$	26,205	$	20,912	$	19,521