Augur Resources has received excellent results from further metallurgical testing of the sulphide mineralization from the Randu Kuning deposit at the Wonogiri project in central Java.
The metallurgical test work investigated gold only recovery process options including gravity separation and cyanide leaching along with other diagnostic leaches. For this test program, two sulphide ore composites were prepared.
One was a ‘low‐grade’ composite containing 0.55 grams/tonne gold, 1.1 grams/tonne silver and 0.23% copper which is typical of the disseminated and stockwork, vein hosted, porphyry‐type mineralization. This returned 71% recovery by gravity of free gold.
The other was a ‘high‐grade’ composite containing 1.26 grams/tonne gold, 1.4 grams/tonne silver and 0.27% copper deemed representative of the higher grade, structurally controlled, breccia/fault hosted (feeder) zones. This returned 50% recovery by gravity of free gold.
Both composites were of a primary, sulphide ore type compiled from core drilled within the conceptual starter pit. Sulphide ore represents over 90% of the resource. The test work was completed in Jakarta, Indonesia at PT Geoservices under the direction of Peter Wallwin of PWA Limited, based in Malaysia.
Tests indicate gravity tails from both composites are non-acid producing, assisting in waste and tailings disposal processes.
Leach tests of gravity tails resulted in average CIL recoverable gold of 83.2% for the low grade ore composite and 83.9% for the high grade composite. No refractory gold is indicated.
Although the results are preliminary they are sufficiently encouraging to warrant further detailed testing. Future test work will investigate optimisation of these tests and also of previous metallurgical test work which investigated recovery of both gold and copper via flotation processing to produce a copper‐gold concentrate.
The flotation results indicated 89.0% recovery of gold and 93.4% recovery of copper to produce a high quality marketable concentrate with grades of up to 21.2% copper and 90.6 grams/tonne gold. The objective of future work is to determine what combination of metallurgical parameters would be most efficient for processing the Randu Kuning gold and copper mineralization.