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Inventories (Tables)
12 Months Ended
Dec. 31, 2020
Classes of current inventories [abstract]  
Summary of inventories
December 31, 2020December 31, 2019
Ore stockpiles$6,327 $3,859 
In-process inventory and finished goods81,120 81,282 
Materials and supplies88,824 78,093 
$176,271 $163,234