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RECEIVABLES (Details)
12 Months Ended
Dec. 31, 2015
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2014
USD ($)
note
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Number of Note Receivables | note     2
Accounts receivable, net, current $ 2,617,000 $ 364,000  
Accounts receivable, net, noncurrent $ 1,096,000 1,146,000  
Financing receivable, principal amount     $ 1,050,000.00
Annual interest rate 3.00%    
Financing receivable, reserve against collectability $ 220,000 220,000  
Trade receivables - mineral concentrate sales      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Accounts receivable, net, current 1,868,000 0  
Trade receivables - other      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Accounts receivable, net, current 749,000 364,000  
Notes receivable and other      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Accounts receivable, net, noncurrent $ 1,096,000 $ 1,146,000