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OPERATING SEGMENT REPORTING (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Operating Segment Reporting
Inventory	$ 34,244			$ 34,244		$ 38,376
Revenue from gold and silver sales	27,395		$ 32,691	77,086	$ 84,657
Production costs applicable to sales	(23,526)		(23,584)	(74,267)	(59,432)
Depreciation and depletion	(4,570)		(7,488)	(16,080)	(17,501)
Gross (loss) profit	(701)		1,619	(13,261)	7,724
Advanced projects	(4,027)		(2,140)	(9,464)	(6,881)
Impairment of mineral property interests and plant and equipment (note 8)		$ (83,800)		(83,805)
Income (Loss) from investment in Minera Santa Cruz S.A. (note 10)	2,582		(328)	(1,139)	(6,775)
Segment (loss) income	(6,569)		(14,544)	(121,398)	(29,649)
General and Administrative and other	(3,361)		887	(8,661)	(7,541)
(Gain) on disposal of fixed assets					(134)
Loss before income and mining taxes	(9,930)		(13,657)	(130,059)	(37,190)
Capital expenditures	594		3,690	9,140	28,179
Other operating				(1,968)
El Gallo Project
Operating Segment Reporting
Inventory	3,100		2,700	3,100	2,700
Production costs applicable to sales				(11,200)	(14,600)
Sunk costs				5,200	5,700
U.S.
Operating Segment Reporting
Depreciation and depletion	(2,099)		(3,790)	(8,527)	(6,510)
Gross (loss) profit	152		631	(9,261)	1,633
Advanced projects	(240)		(46)	(789)	(632)
Impairment of mineral property interests and plant and equipment (note 8)				(83,805)
Segment (loss) income	(2,483)		(3,668)	(100,480)	(5,154)
Capital expenditures	106		1,190	4,712	17,804
Other operating				(1,390)
Canada
Operating Segment Reporting
Depreciation and depletion	(2,404)		(3,589)	(7,336)	(10,520)
Gross (loss) profit	(926)		8	(4,310)	1,594
Advanced projects	(2,784)		(384)	(5,609)	(384)
Segment (loss) income	(4,899)		(9,067)	(14,931)	(13,964)
Capital expenditures	488		2,500	4,428	10,375
Other operating				(578)
Mexico
Operating Segment Reporting
Depreciation and depletion	(67)		(109)	(217)	(471)
Gross (loss) profit	73		980	310	4,497
Advanced projects	(1,003)		(1,710)	(3,066)	(5,865)
Segment (loss) income	(1,357)		(732)	(3,219)	(1,370)
MSC
Operating Segment Reporting
Income (Loss) from investment in Minera Santa Cruz S.A. (note 10)	2,582		(328)	(1,139)	(6,775)
Segment (loss) income	2,582		(328)	(1,139)	(6,775)
Los Azules
Operating Segment Reporting
Segment (loss) income	(412)		(749)	(1,629)	(2,386)
MSC
Operating Segment Reporting
Revenue from gold and silver sales	70,195		74,530	154,666	189,348
Production costs applicable to sales	(41,512)		(43,345)	(100,230)	(119,392)
Depreciation and depletion	(7,107)		(18,158)	(22,084)	(50,083)
Gross (loss) profit	21,576		13,027	32,352	19,873
Income (Loss) from investment in Minera Santa Cruz S.A. (note 10)	2,582		(328)	(1,139)	(6,775)
Loss before income and mining taxes	12,253		6,151	6,846	3,574
Gold and silver sales
Operating Segment Reporting
Revenue from gold and silver sales	27,395		32,691	77,086	84,657
Gold and silver sales | U.S.
Operating Segment Reporting
Revenue from gold and silver sales	13,042		16,577	38,129	28,941
Gold and silver sales | Canada
Operating Segment Reporting
Revenue from gold and silver sales	10,352		11,147	27,257	36,139
Gold and silver sales | Mexico
Operating Segment Reporting
Revenue from gold and silver sales	4,001		4,967	11,700	19,577
Production costs applicable to sales
Operating Segment Reporting
Production costs applicable to sales	(23,526)		(23,584)	(74,267)	(59,432)
Production costs applicable to sales | U.S.
Operating Segment Reporting
Production costs applicable to sales	(10,791)		(12,156)	(38,863)	(20,798)
Production costs applicable to sales | Canada
Operating Segment Reporting
Production costs applicable to sales	(8,874)		(7,550)	(24,231)	(24,025)
Production costs applicable to sales | Mexico
Operating Segment Reporting
Production costs applicable to sales	(3,861)		(3,878)	(11,173)	(14,609)
Exploration
Operating Segment Reporting
Production costs applicable to sales	(4,423)		(13,695)	(11,761)	(23,717)
Exploration | U.S.
Operating Segment Reporting
Production costs applicable to sales	(2,395)		(4,253)	(5,235)	(6,155)
Exploration | Canada
Operating Segment Reporting
Production costs applicable to sales	(1,189)		(8,691)	(4,434)	(15,174)
Exploration | Mexico
Operating Segment Reporting
Production costs applicable to sales	(427)		(2)	(463)	(2)
Exploration | Los Azules
Operating Segment Reporting
Production costs applicable to sales	$ (412)		$ (749)	$ (1,629)	$ (2,386)

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