Alto Metals Ltd’s (ASX:AME) preliminary test-work of Lord Nelson primary zone mineralisation within the Sandstone Gold Project in WA has returned "excellent" average gold recoveries of 96%.
This adds to gold recoveries of greater than 93% in oxide and transitional zone mineralisation obtained in previous metallurgical test-work at Lord Nelson.
These results are in line with expectations based on historical performance at the Lord Nelson mine where Troy Resources Ltd (ASX:TRY) reported production plant gold recovery of between 93% to 96%.
Alto managing director Matthew Bowles said: “The excellent gold recoveries achieved from recent preliminary cyanide leach test-work at Lord Nelson, complements the high gold recoveries at our other deposits and those reported for Lord Nelson from previous metallurgical test-work and historical processing records by Troy Resources.”
Conventional cyanide extraction
Test-work carried out on four RC drill samples within primary zone mineralisation with gold grades ranging from around 3 g/t to 11 g/t, all reported in excess of 95% gold recovery with an average of 96%.
Bowles said: “Whilst we remain focused on exploration and resource growth at the Sandstone Gold Project, it is pleasing to report that test-work to date is in-line with our expectations and demonstrates the mineralisation within our current mineral resources is amenable to conventional cyanide extraction methods.”
Other prospect recoveries
In 2018 and 2019 the company announced maiden mineral resource estimates for the Vanguard Camp, Indomitable Camp, Havilah and Ladybird deposits.
As part the Mineral Resource estimation, Alto collected and submitted a total of 25 samples to Intertek Genalysis for Accelerated Cyanide Leach LeachWELLTM testwork.
Gold recoveries averaging greater than 92% from accelerated cyanide leach test-work at Indomitable, Tiger Moth, Vanguard, Havilah and Ladybird indicate that these deposits are also amenable to conventional cyanide extraction methods.
Historical mining
Troy mined the Lord Nelson deposit as an open pit mine to around 90 metres below surface between 2005 and 2010 and recovered 207,000 ounces at 4.6 g/t gold.
That company reported that recovery of gold at the Sandstone plant typically ranged from 93% to 96% with total recovery in the period July 2006 to end of June 2007 of 94.4%.
Previous test-work by Troy Resources determined:
- Lord Nelson ore was found to be free milling;
- Gravity gold recovery was found to be required to prevent coarse gold entering the leach circuit and being partially lost to the tailings and it was estimated that over 20% of total gold could be recovered as concentrate from the oxide ore and close to 40% for the transitional ore; and
- Acceptable gold recoveries of greater than 93% for oxide and transitional ores were obtained after 24 hours of direct cyanide leaching.
Upcoming exploration
Multiple drill-ready targets will be tested for repeat lodes, with an initial 5,000 metres of a planned 30,000 metres RC drill program due to start this week.
Alto recently secured commitments to raise $5.5 million in a placement and intends to aggressively advance exploration along the entire 3-kilometre Lords’ Corridor and drill test a number of regional targets within the +800 square kilometre Sandstone Gold Project.