Property, Plant and Equipment, Net (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Property, plant and equipment
Property, plant and equipment, gross	$ 50,206	$ 50,521
Less: Accumulated depreciation and amortization	(19,567)	(18,146)
Property, plant and equipment, net	30,639	32,375
Mining Properties And Mineral Rights [Member]
Property, plant and equipment
Property, plant and equipment, gross	22,397	22,397
Exploration Properties [Member]
Property, plant and equipment
Property, plant and equipment, gross	2,993	2,993
Royalty Properties [Member]
Property, plant and equipment
Property, plant and equipment, gross	200	200
Building [Member]
Property, plant and equipment
Property, plant and equipment, gross	2,357	2,349
Machinery And Equipment [Member]
Property, plant and equipment
Property, plant and equipment, gross	19,416	19,441
Office Equipment [Member]
Property, plant and equipment
Property, plant and equipment, gross	841	1,054
Asset Retirement Obligation Costs [Member]
Property, plant and equipment
Property, plant and equipment, gross	$ 2,002	$ 2,087