Property, Plant, and Equipment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2012
Property, plant and equipment, net [Abstract]
Property, plant, and equipment, gross	$ 555,466		$ 543,955
Less accumulated depreciation, depletion and amortization	(122,570)		(111,194)
Property, plant, and equipment, net	432,896		432,761
Depreciation [Abstract]
Depreciation expense	11,683	7,300
Depreciation expense recorded in cost of goods sold	11,502	7,106
Depreciation expense recorded in selling and general administrative expenses	181	194
Capitalized interest	0	12
Land, Land Improvements, and Land Use Rights [Member]
Property, plant and equipment, net [Abstract]
Property, plant, and equipment, gross	10,561		10,831
Building and Improvements [Member]
Property, plant and equipment, net [Abstract]
Property, plant, and equipment, gross	76,992		76,395
Machinery and Equipment [Member]
Property, plant and equipment, net [Abstract]
Property, plant, and equipment, gross	180,182		175,305
Furnaces [Member]
Property, plant and equipment, net [Abstract]
Property, plant, and equipment, gross	195,245		193,055
Mineral Reserves [Member]
Property, plant and equipment, net [Abstract]
Property, plant, and equipment, gross	55,843		55,843
Mine Development [Member]
Property, plant and equipment, net [Abstract]
Property, plant, and equipment, gross	4,512		4,058
Other [Member]
Property, plant and equipment, net [Abstract]
Property, plant, and equipment, gross	4,916		4,852
Construction in Progress [Member]
Property, plant and equipment, net [Abstract]
Property, plant, and equipment, gross	$ 27,215		$ 23,616