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Inventories (Tables)
9 Months Ended
Sep. 30, 2022
Inventory Disclosure [Abstract]  
Schedule of Inventories
Inventories are summarized as follows:
 SEPTEMBER 30
2022
 DECEMBER 31
2021
Coal$20,751 $19,352 
Mining supplies41,048 34,733 
 Total inventories$61,799  $54,085