Evolution Mining says it is embarking on a prefeasibility study to further expand its Cowal open-pit mine as part of a plan to build towards 350,000 oz/y of sustainable, reliable, low-cost gold production from the New South Wales operation.
Currently on the E42 stage H cutback, Evolution said during a recent site visit that there is potential to further the life of the open pit by accessing feed from the E41 and E46 satellite pits. The study looking into a possible expansion is due later this year, with the company saying it could provide long-term base load ore feed for the operation.
The mine produced 262,000 ounces in Evolution’s 2020 financial year.
The Stage H cutback the company is currently pursuing is expected to see increased ore volumes and grade mined in the first six months of this year, with the strip ratio to fall below 1:1 in its 2023 financial year, Evolution said. It also says an equipment strategy review is underway, with opportunities to “rationalise fleet” with reduced re-handling.
The haulage and loading fleet at Cowal currently consists of 20 Cat 789C dump trucks, three Cat 785C trucks, four excavators (one Liebherr 9400, one Liebherr 994B, one Liebherr 9200 and one Hitachi EX1200), plus three Cat 992G wheel loaders. It also has six hired Epiroc SmartROC surface drills at the operation, one Drill Rigs Australia GC600 drill rig, five Cat D10T tracked dozers and one Cat 834H wheel dozer.
The open-pit expansion is only part of the expansion story at Cowal, with a feasibility study underway on an underground operation. This is factoring in 3 Moz of resources and 1 Moz of reserves, with high-grade orebodies open at depth, the company says.
A second decline (Galway) is due to be developed at Cowal this year, with diamond drilling set to commence next month. The 14,300 m of planned drilling will, the company says, help confirm optimal grade control parameters and convert resources to reserves.
Evolution Mining also has a permit to increase processing capacity at Cowal to 9.8 Mt/y, with near-term incremental improvements targeting a circa-9 Mt/y rate.
The process flowsheet at Cowal includes primary crushing with a Metso Outotec 54-75 Superior MK-II gyratory, grinding with an FLSmidth 36 ft (11 m) x 20.5 ft (6.2 m) SAG mill and FLSmidth 22 ft x 36.5 ft ball mill, and screening with Schenck and Delkor screens. Sandvik H6800 hydroconecone crushers, Metso Outotec flotation cells, a Metso Outotec Vertimill, and Metso Outotec stirred media detritors also feature.
Evolution also said it is testing technology that uses glycine and cyanide during the cyanidation process of gold ore at Cowal for potential significant cost savings and environmental benefits.
Lab trials with the GlyCat™ technology from Australia-based Mining and Process Solutions have been completed successfully, it said, with the next phase being pilot plant trials to assess variability tests and long-term environmental impacts.
