Metallurgical testwork at Alto Metals Ltd (ASX:AME)’s 100% owned Sandstone Gold Project in Western Australia has returned what the company describes as “excellent” gold recoveries, further derisking the project and its Indomitable deposit.
The company engaged Independent Metallurgical Operations Pty Ltd to manage sighter metallurgical testwork on composite reverse circulation (RC) drill samples from the Indomitable deposit, which revealed gold recovery of up to 97% from gravity separation and cyanide leaching.Results also included high gravity gold recovery of 64.8%.
Gold recoveries at a coarse grind size of 150 µm were:
- 89.4% of gold within 2 hours,
- 94.3% of gold within 4 hours,
- 96.1% of gold within 8 hours, and
- 97% of gold within 24 hours.
The results are complementary to previous LeachwellTM accelerated cyanide leach on oxide RC drill samples, which reported 93% gold recovery from Indomitable. Importantly, the test work completed to date indicates all deposits within the Sandstone Gold Project are amenable to conventional cyanide extraction.
“This latest metallurgical testwork carried out on samples from our Indomitable deposit demonstrates that primary mineralisation within the fresh rock has excellent overall recoveries including a high gravity gold component,” said Alto managing director Matthew Bowles.
“Importantly, the test work confirms the material can be processed using conventional gravity and cyanide leaching, further de-risking the Indomitable deposit and the Sandstone Gold Project.”
Extensional drilling underway
The Sandstone Gold Project covers more than 740 square kilometres of the Sandstone Greenstone Belt in WA. The project currently has an open pit gold resource of 17.6 million tonnes at 1.5 g/t gold for 832,000 ounces, constrained within A$2,500 per ounce pit-shells capturing over 80% of the total unconstrained mineral resource estimate of 23.5 million tonnes at 1.4 g/t gold for 1.05 million ounces.
An RC drilling program of about 3,500 metre is now underway at Sandstone to test extensional targets outside the current mineral resources at the Vanguard, Ladybird and Bull Oak gold deposits. The program also includes first-pass drilling at the new Lightning Prospect.