CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (9,688)	$ (34,618)
Adjustments to reconcile net loss for the period to net cash used in operating activities:
Non-cash portion of interest expense - Note 9	4,439	17,020
Non-cash gain on fair value adjustment for warrant liabilities - Note 11	(9,493)	0
Write-down of production inventories - Note 4	0	6,965
Depreciation and amortization	1,568	1,876
Stock-based compensation - Note 15	538	365
Accretion - Note 12	102	93
Phantom share compensation	0	263
Changes in operating assets and liabilities:
Accounts receivable	412	(754)
Production-related inventories	(3,970)	(10,935)
Materials and supplies inventories	167	(332)
Prepaids and other assets, current and non-current	(1,268)	(1,604)
Accounts payable	1,800	2,409
Other liabilities, current and non-current	632	254
Interest payable	0	(447)
Net cash used in operating activities	(14,761)	(19,445)
Cash flows used in investing activities:
Additions to plant, equipment, and mine development	(5,082)	(2,090)
Net cash used in investing activities	(5,082)	(2,090)
Cash flows from financing activities:
Repayment of First Lien Agreement - Note 9	0	(632)
Transaction and issuance costs	0	(2,610)
Proceeds from debt issuances, net of debt issuance costs	0	24,900
Net cash provided by financing activities	0	21,658
Net (decrease) increase in cash and restricted cash	(19,843)	123
Cash and restricted cash, beginning of period	96,040	48,967
Cash and restricted cash, end of period	76,197	49,090
Reconciliation of cash and restricted cash:
Cash	36,497	6,566
Restricted cash - current	0	2,929
Restricted cash - non-current	39,700	39,595
Total cash and restricted cash	$ 76,197	$ 49,090