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IMPAIRMENTS (Details) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]      
Impairment of plant and equipment and mineral properties $ 0    
Impairment of assets to be abandoned of $ 0 $ 0 $ 3,799,000