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Long-Term Reclamation Liability and Retirement Obligation Asset - Reconciliation of Aggregate Retirement Asset (Details) - USD ($)
3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Retirement obligation asset — beginning of period $ 282,745 $ 617,126
Additional obligations incurred 0 0
Amortization of retirement obligation asset (14,917) (334,381)
Retirement obligation asset — end of period $ 267,828 $ 282,745