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NATURE OF OPERATIONS AND BASIS OF PRESENTATION (Details)	6 Months Ended
	Jun. 30, 2021
Nature of operations and recent accounting pronouncements
Ownership interests in various mines (as a percent)	100.00%
Ownership interest (as a percent)	49.00%
MSC | Equity Method Investment
Nature of operations and recent accounting pronouncements
Ownership interest (as a percent)	49.00%

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- Definition

The Company's ownership interests in various mines.

+ References

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

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