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INVENTORIES | 3 Months Ended
--- | ---
Mar. 31, 2020
INVENTORIES |
INVENTORIES | 7.INVENTORIES ​ Inventories consist of the following: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | March 31, | ​ | December 31, | ​
​ | ​ | 2020 |  | 2019 |
​ | ​ | (in thousands) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Coal | ​ | $ | 86,871 | ​ | $ | 63,645 | ​
Supplies (net of reserve for obsolescence of $5,839 and $5,555, respectively) | ​ |  | 37,645 | ​ |  | 37,660 | ​
Total inventories, net | ​ | $ | 124,516 | ​ | $ | 101,305 | ​
​ During the three months ended March 31, 2020, we recorded a lower of cost or net realizable value adjustment of $5.4 million to our coal inventories as a result of lower coal sale prices resulting from challenging market conditions and higher cost per ton primarily attributed to various factors lowering production and thus impacting our fixed costs per ton in addition to the impact of challenging market conditions on our production levels. The lower of cost or net realizable value adjustments were primarily attributable to the Hamilton mining complex. ​

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- Definition The entire disclosure for inventory. Includes, but is not limited to, the basis of stating inventory, the method of determining inventory cost, the classes of inventory, and the nature of the cost elements included in inventory. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -URI http://asc.fasb.org/topic&trid=2126998 + Details
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