Note 3 - Property, Plant and Equipment (Tables)

6 Months Ended

Jun. 30, 2020

Property, Plant and Equipment [Abstract]

Schedule of property, plant, and equipment

(In thousands)	June 30, 2020		December 31, 2019
Plant and equipment	$	154,337	$	142,773
Construction in process		6,650		11,986
Capitalized mine development cost		67,831		58,773
Less: accumulated depreciation and amortization		(45,673)		(35,330)
Total property, plant and equipment, net	$	183,145	$	178,202

Schedule of depreciation and amortization

	Three months ended June 30,				Six months ended June 30,
(In thousands)	2020		2019		2020		2019
Depreciation of plant and equipment	$	4,240	$	3,416	$	8,415	$	6,436
Amortization of capitalized
mine development costs		1,101		1,406		1,928		2,502
Total depreciation and amortization	$	5,341	$	4,822	$	10,343	$	8,938