FINANCIAL INFORMATION BY INDUSTRY SEGMENT AND PRODUCT LINE (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) Segment	Jun. 30, 2016 USD ($)
FINANCIAL INFORMATION BY INDUSTRY SEGMENT AND PRODUCT LINE [Abstract]
Number of segments | Segment			1
Revenue from External Customer [Line Items]
Revenue	$ 127,957	$ 108,152	$ 370,395	$ 307,765
Tungsten Slurries [Member]
Revenue from External Customer [Line Items]
Revenue	54,731	46,559	161,867	134,856
Dielectric Slurries [Member]
Revenue from External Customer [Line Items]
Revenue	30,266	25,348	87,391	72,045
Polishing Pads [Member]
Revenue from External Customer [Line Items]
Revenue	17,599	16,048	50,947	46,586
Other Metals Slurries [Member]
Revenue from External Customer [Line Items]
Revenue	16,090	14,065	46,540	36,517
Engineered Surface Finishes [Member]
Revenue from External Customer [Line Items]
Revenue	7,806	4,382	18,866	12,077
Data Storage Slurries [Member]
Revenue from External Customer [Line Items]
Revenue	$ 1,465	$ 1,750	$ 4,784	$ 5,684