Note 3 - Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Less accumulated depreciation and amortization	$ (15,809)	$ (3,406)
Total property, plant and equipment, net	149,205	115,451
Plant and Equipment, at Cost [Member]
Property, plant and equipment, gross	109,911	80,455
Construction in Progress [Member]
Property, plant and equipment, gross	12,066	7,626
Mine Development [Member]
Property, plant and equipment, gross	$ 43,037	$ 30,776