Marmota reports exceptional gold recoveries from metallurgical testing at Aurora Tank
Marmota (ASX: MEU) has reported gold recoveries of up to 93% from metallurgical testing at the Aurora Tank heap leach operation in the Gawler Craton.
Australian Minmet Metallurgical Laboratories (AMML) carried out the test work on 31 sub-composites representing 197 metres of drill core in partnership with a heap leaching team from Kappes Cassiday & Associates.
The company achieved rapid leaching on all columns with over 55% gold extraction within the first 10 days.
Composite samples
The program consisted of head assays, sizing analyses with fraction assays, 10-day two-stage intermittent bottle roll tests at 12.5 millimetres and 8mm, ground ore diagnostic leach tests and agglomeration to assess column leach testing.
It used a variety of different composite samples from Aurora Tank, distinguished primarily by different weathering profiles, crush sizes and leach durations.
The moderately weathered master composite (MC)-1 sample yielded an “exceptional” gold extraction of 93% in 59 days of leaching at 8-millimetre crush size, while the partially weathered MC-2 yielded 83% extraction at 12.5mm across 87 days and 86% extraction at 8mm in an extended 159-day leach cycle.
AMML said crush sizes coarser than 12.5mm are likely to produce similar leach behaviour for the weathered materials.
Silver values
In addition to the strong gold recoveries, all samples returned silver values averaging less than 0.5 grams per tonne along with low values of contained copper, mercury and sulphur.
Marmota expects these to have a minor impact on recovery plant design and operation.
The company plans to conduct physical testing of whole core pieces, which will include bond crushing work index and abrasion index measurements.
Long process
Marmota chair Dr Colin Rose said metallurgical testing had been a long but beneficial process.
“Aurora Tank features multiple bonanza grades, predominantly close to surface with soft ground and outstanding metallurgy amenable to low-cost, low-capex heap leach recovery,” he said.
“We are extremely fortunate to own all the gold deposits within a 10,000 square kilometre hub of the Gawler Craton just as gold is booming to record highs.”
Dr Rose said the column leach results presented Marmota with an “attractive commercial option” for processing Aurora Tank ore without the expense and complexities of a carbon-in-leach plant and tailings dam construction.