Inventories, net (Details)		3 Months Ended		6 Months Ended
		Jun. 30, 2020 USD ($) $ / oz	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) $ / oz	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Stockpiles - underground mine		$ 520,000		$ 520,000		$ 3,968,000
Stockpiles - open pit mine		321,000		321,000		833,000
Leach pad		15,227,000		15,227,000		9,103,000
Concentrates		1,937,000		1,937,000		1,340,000
Dore	[1]	1,879,000		1,879,000		1,581,000
Subtotal - product inventories		19,884,000		19,884,000		16,825,000
Materials and supplies	[2]	7,150,000		7,150,000		7,306,000
Total		27,034,000		27,034,000		24,131,000
Low-grade ore stockpile inventory		4,000,000.0		4,000,000.0		4,700,000
Dore
Inventory reserve		378,000		378,000		478,000
Materials And Supplies [Member]
Inventory reserve		$ 1,264,000		$ 1,264,000		$ 1,264,000
Isabella Pearl Project
Carrying value per ounce | $ / oz		1,768		1,768
Inventory adjustment		$ 2,000,000.0	$ 0	$ 3,600,000	$ 0

[1] Net of reserve of $378 and $478 at June 30, 2020 and December 31, 2019, respectively.

[2] Net of reserve for obsolescence of $1,264 as of June 30, 2020 and December 31, 2019.