MAJOR SOURCES OF REVENUE (Details) - Sales Revenue - Customer Concentration Risk - USD ($) $ in Thousands	12 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Centerra
Major sources of revenue
Revenue	$ 133,534	$ 136,737	$ 125,438
Percentage of total revenue	29.10%	31.00%	34.90%
Barrick
Major sources of revenue
Revenue	$ 108,285	$ 104,009	$ 49,683
Percentage of total revenue	23.60%	23.60%	13.80%
Teck
Major sources of revenue
Revenue	$ 57,413	$ 60,251	$ 49,243
Percentage of total revenue	12.50%	13.70%	13.70%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611

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