SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue, fixed assets (Details)	3 Months Ended		9 Months Ended
	Oct. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Oct. 31, 2019 USD ($) item contract MT	Oct. 31, 2018 USD ($)	Jan. 31, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Royalty Revenue	$ 6,488,299	$ 13,891,273	$ 26,151,926	$ 39,663,012
Base overriding royalties, first tier portion percentage			90.00%
Base overriding royalties, first tier shipment ceiling (in million tons) | MT			4
Base overriding royalties, second tier portion percentage			85.00%
Base overriding royalties, second tier shipment ceiling (in million tons) | MT			2
Base overriding royalties, third tier portion percentage			25.00%
Base overriding royalties, third tier shipment threshold (in million tons) | MT			6
Base overriding royalties, number of volume thresholds for transaction price | item			4
Base overriding royalties, volume threshold for transaction price | MT			1
Accrued income receivable	2,408,279		$ 2,408,279		$ 2,339,060
Number of customer contracts resulting in net contract liability | contract			1
Contract liability, net	938,129		$ 938,129
Contract asset before netting	1,294,821		1,294,821
Contract liability before netting	2,232,950		2,232,950
Contract asset, net					$ 56,357
Base Overriding Royalties
Revenue from Contract with Customer [Abstract]
Royalty Revenue	3,674,830	8,349,255	15,069,353	23,652,703
Bonus Royalties
Revenue from Contract with Customer [Abstract]
Royalty Revenue	2,640,101	5,422,575	10,565,280	15,572,478
Fee Royalties
Revenue from Contract with Customer [Abstract]
Royalty Revenue	$ 173,368	$ 119,443	$ 517,293	$ 437,831