SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2021 USD ($) segment	Mar. 31, 2020 USD ($)	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	$ 2,224,435		$ 2,224,435		$ 2,318,913
Revenue	142,589	$ 136,437	447,829	$ 378,853
Cost of sales	21,469	21,961	68,230	63,149
Production taxes	1,835	851	4,591	2,934
Depletion	41,202	51,115	135,276	129,758
Total segment gross profit	78,083	62,510	239,732	183,012
Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	825,716		825,716		892,587
Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	375,235		375,235		406,469
Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	488,073		488,073		501,583
Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	283,542		283,542		215,784
Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	69,440		69,440		75,951
United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	114,776		114,776		159,445
Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	28,484		28,484		30,006
Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	39,169		39,169		37,088
Stream interests
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	1,578,784		1,578,784		1,614,363
Revenue	95,346	97,460	309,568	274,065
Cost of sales	21,469	21,961	68,230	63,149
Depletion	32,595	43,240	111,848	106,883
Total segment gross profit	41,282	32,259	129,490	104,033
Stream interests | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	644,334		644,334		702,732
Revenue	42,609	37,136	138,497	112,990
Stream interests | Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	375,235		375,235		406,469
Revenue	30,173	28,302	88,998	73,534
Stream interests | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	263,957		263,957		277,661
Revenue	13,022	22,055	54,296	63,323
Stream interests | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	283,221		283,221		215,463
Revenue	9,542	9,967	27,777	24,218
Stream interests | Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	12,037		12,037		12,038
Royalty interests
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	645,651		645,651		704,550
Revenue	47,243	38,977	138,261	104,788
Production taxes	1,835	851	4,591	2,934
Depletion	8,607	7,875	23,428	22,875
Total segment gross profit	36,801	30,251	110,242	78,979
Royalty interests | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	181,382		181,382		189,855
Revenue	8,612	3,714	22,069	11,062
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	748	925	2,241	2,531
Royalty interests | Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	69,440		69,440		75,951
Revenue	15,270	9,126	42,021	26,084
Royalty interests | United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	114,776		114,776		159,445
Revenue	16,474	13,199	47,262	33,813
Royalty interests | Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	28,484		28,484		30,006
Revenue	4,360	9,160	17,217	24,923
Royalty interests | Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	27,132		27,132		$ 25,050
Revenue	$ 1,779	$ 2,853	$ 7,451	$ 6,375