Orsa Ventures Corp. (TSXV:ORN) reported that its consultants, JDS Energy and Mining Inc., have completed a detailed review of metallurgical studies that confirm that oxide mineralization responds well to cyanidation. It is the opinion of Orsa’s consultant’s that sulphide mineralization may be economically recovered by milling and cyanidation. Testwork to refine a process would include testing for crush and grind size, mineralogy, flotation, leaching, and settling and filtration.
As quoted in the press release:
Column leach testing indicated recoveries between 74 to 88 percent on oxidized tuff and rhyolite.
Column testwork indicated that a crush size of minus 1/2 inch was determined to be the optimum size for the four basic rock types that represented the deposit for heap leaching. The expected gold recoveries by rock type are as follows:
- Tuff – 77%
- Rhyolite – 74%
- Quartz Butte Rhyolite – 88%
- Basalt – 62%
Tests on sulphide mineralization prior to Pegasus’ involvement included cyanide leaching at various particle sizes and preparative floatation testing. Gold recoveries ranged from 15% for heap leach sized material up to 70% for selected finely ground rock types. Flotation gold recoveries averaged 60-70% with concentrate grades of 1-2 oz/t gold.