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Components of Deferred Tax Assets and Liabilities (Detail) (USD $)
Jun. 30, 2012
Dec. 31, 2011
Schedule of Deferred Tax Assets and Liabilities [Line Items]    
Deferred tax liabilities      
Deferred tax assets:    
Allowance for obsolete and slow-moving inventories 3,704 3,718
Impairment on property, plant and equipment 636,615 639,031
Property, plant and equipment 68,523 81,060
Property, plant and equipment under capital leases (23,989) (8,001)
US federal net operating loss 10,442,134 10,111,821
Total deferred tax assets 13,009,580 12,850,004
Valuation allowance (10,442,134) (10,111,821)
Net deferred tax asset 2,567,446 2,738,183
Current deferred tax asset 105,583 228,702
Long-term deferred tax asset 2,461,863 2,509,481
Exploration costs
    
Deferred tax assets:    
Other deferred tax assets 1,780,714 1,797,391
Repair and maintenance costs
    
Deferred tax assets:    
Other deferred tax assets $ 101,879 $ 224,984