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Property, Plant and Mine Development, net - Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
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Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Property, Plant and Mine Development, net |  |  |  |
Depreciation and amortization expense | $ 3,521 | $ 4,340 | $ 11,299 | $ 13,537

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- Definition Amount of expense for allocation of cost of tangible and intangible assets over their useful lives, and reduction in quantity of natural resource due to consumption directly used in production of good and rendering of service. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(b)(2)) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 + Details
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- References No definition available. + Details
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