Note 3 - Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Schedule of property, plant, and equipment

	December 31,
(In thousands)	2019		2018
Plant and equipment	$	142,773	$	109,911
Construction in process		11,986		12,066
Capitalized mine development cost		58,773		43,037
Less: accumulated depreciation and amortization		(35,330)		(15,809)
Total property, plant and equipment, net	$	178,202	$	149,205

Schedule of depreciation and amortization

	Year ended December 31,
(In thousands)	2019		2018		2017
Depreciation of plant and equipment	$	14,219	$	9,751	$	2,618
Amortization of capitalized
mine development costs		5,302		2,672		536
Total depreciation and amortization	$	19,521	$	12,423	$	3,154