Note 3 - Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, plant, and equipment
Less: Accumulated depreciation and amortization	$ (35,330)	$ (15,809)
Total property, plant and equipment, net	178,202	149,205
Plant and Equipment
Property, plant, and equipment
Property, plant and equipment, gross	142,773	109,911
Construction in Progress
Property, plant, and equipment
Property, plant and equipment, gross	11,986	12,066
Capitalized mine development cost
Property, plant, and equipment
Property, plant and equipment, gross	$ 58,773	$ 43,037