REVENUE AND COST OF SALES (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue And Cost Of Sales
Concentrate sales	$ 31,417	$ 34,551	$ 33,327
Provisional pricing adjustments	329	(435)	32
Total Revenue	$ 31,746	$ 34,116	$ 33,359

The income arising in the course of an entity's ordinary activities. Income is increases in economic benefits during the accounting period in the form of inflows or enhancements of assets or decreases of liabilities that result in an increase in equity, other than those relating to contributions from equity participants.

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+ Details