SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Jun. 30, 2020 USD ($)
Long Lived Assets and Pre-Tax Income by Geographical Information
Number of reportable segments | segment			2
Stream and royalty interests, net	$ 2,231,980		$ 2,231,980		$ 2,318,913
Revenue	158,360	$ 123,643	305,240	$ 242,417
Cost of sales	24,859	21,077	46,760	41,188
Production taxes	1,401	984	2,756	2,083
Depletion	47,861	39,982	94,075	78,643
Total segment gross profit	84,239	61,600	161,649	120,503
Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	845,773		845,773		892,587
Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	384,322		384,322		406,469
Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	491,450		491,450		501,583
Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	254,177		254,177		215,784
Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	71,843		71,843		75,951
United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	115,427		115,427		159,445
Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	29,161		29,161		30,006
Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	39,827		39,827		37,088
Stream interests
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	1,578,722		1,578,722		1,614,363
Revenue	107,719	89,625	214,222	176,606
Cost of sales	24,859	21,077	46,760	41,188
Depletion	40,226	32,181	79,253	63,643
Total segment gross profit	42,634	36,367	88,209	71,775
Stream interests | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	661,172		661,172		702,732
Revenue	54,302	38,191	95,888	75,854
Stream interests | Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	384,322		384,322		406,469
Revenue	27,554	23,614	58,824	45,232
Stream interests | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	267,334		267,334		277,661
Revenue	17,766	20,665	41,275	41,269
Stream interests | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	253,856		253,856		215,463
Revenue	8,097	7,155	18,235	14,251
Stream interests | Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	12,038		12,038		12,038
Royalty interests
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	653,258		653,258		704,550
Revenue	50,641	34,018	91,018	65,811
Production taxes	1,401	984	2,756	2,083
Depletion	7,635	7,801	14,822	15,000
Total segment gross profit	41,605	25,233	73,440	48,728
Royalty interests | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	184,601		184,601		189,855
Revenue	6,047	8,037	13,458	16,958
Royalty interests | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	224,116		224,116		223,922
Royalty interests | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	321		321		321
Revenue	744	911	1,494	1,606
Royalty interests | Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	71,843		71,843		75,951
Revenue	15,174	9,376	26,751	15,763
Royalty interests | United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	115,427		115,427		159,445
Revenue	17,090	10,012	30,788	20,614
Royalty interests | Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	29,161		29,161		30,006
Revenue	8,314	3,546	12,856	7,348
Royalty interests | Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	27,789		27,789		$ 25,050
Revenue	$ 3,272	$ 2,136	$ 5,671	$ 3,522