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Significant Accounting Policies - Depreciation (Details) | 12 Months Ended
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Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
Depreciation and amortization expense included in operations |  |  |
Depreciation and amortization expense included in operations | $ 151,000 | $ 176,000 | $ 188,000
Depletion of mineral rights | $ 514,000 | $ 510,000 | $ 650,000
Office and field equipment useful lives minimum(Years) | 5 |  |
Office and field equipment useful lives maximum(Years) | 30 |  |

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- Definition Depletion of mineral rights + References No definition available. + Details
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Namespace Prefix: | fil_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Depreciation and amortization expense included in operations + References No definition available. + Details
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Namespace Prefix: | fil_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | fil_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Office and field equipment useful lives maximum(Years) + References No definition available. + Details
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Namespace Prefix: | fil_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

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- Definition Office and field equipment useful lives minimum(Years) + References No definition available. + Details
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Namespace Prefix: | fil_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration