Property, Plant and Mine Development (Tables)

3 Months Ended

Mar. 31, 2016

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Mine Development

At March 31, 2016 and December 31, 2015, property, plant and mine development (in thousands) consisted of the following:

	March 31,   2016			December 31,    2015
Mining property and mine development	$	222,427		$	222,439
Asset retirement cost	9,887			9,889
Land	30,322			30,322
Land improvements	37,972			37,791
Buildings	51,280			51,280
Machinery and equipment	368,353			360,817
Furniture and fixtures	1,917			1,917
Construction-in-progress	53,867			56,130
	776,025			770,585
Accumulated depletion, depreciation and amortization	(223,020		)	(209,389		)
Total property, plant and mine development, net	$	553,005		$	561,196