Brief History

The Mt Garnet processing plant was commissioned early 2003 by Kagara Zinc (Kagara). In 2012, CSD purchased the Mt Garnet base metal mill and associated tenements from SPM, who in turn purchased from the Administrators appointed for Kagara Limited.

CSD (On behalf of SPM) commenced base metal mining in December 2013 with ore haulage to Mt Garnet from DRS. Mt Garnet mill produced polymetallic (Zn, Pb, Cu) concentrate from March 2014 through to July 2016 before the site entered temporary care and maintenance.

Mining and processing resumed in January 2017.

The Mt Garnet processing plant is capable of processing up to one million tonnes of ore per annum. It is currently operating at a target of 70 tonnes per hour in the polymetallic circuit. The Mount Garnet Processing Plant currently produces approximately 150 tonnes a day of zinc, lead and copper concentrates with silver and gold co-product.

The Mount Garnet Processing Plant is progressing towards a steady state of production with a significant increase in ore processed.

The process plant is located adjacent to the Mount Garnet township with all modern infrastructure and operates on power from the grid.

Operation

A front-end loader (FEL) feeds ore from the ROM pad into a jaw crusher at a rate of approximately 200 t/h where it is crushed to less than 100 mm and then stockpiled on the Fine Ore Stockpile (FOS) via conveyor system. This material is then fed to the milling circuit via three feeders and a conveyor for further size reduction. The milling circuit consists of an open circuit semi-autogenous grinding (SAG) mill and a closed circuit ball mill, with a final product of approximately P80 of 100 µm that is fed to the flotation circuit at approximately 35% solids and a capacity of up to 70 t/h (dependant on feed quality).

The flotation circuit consists of multiple banks of flotation cells arranged in rougher/scavenger and cleaner configuration, with sequential copper, lead and zinc circuits, with the tailings from the copper scavenger being the feed to the lead flotation circuit and the tailings from the lead scavenger acting as the feed to the zinc flotation circuit. All three circuits have the pH controlled with lime, though different chemicals are added to each circuit to enhance the selectivity of the metal being floated in that particular circuit.

The Online Stream Analyser (OSA) system helps operators achieve the target grades for each concentrate, (being 25% Cu concentrate, 66% Pb concentrate and 48% Zn concentrate), by measuring the grade of many streams via X-Ray Fluorescence (XRF) which is then reported to the operations team and the data used to make adjustments to the various circuit parameters. The target recoveries are approximately 60% for Cu, 68% for Pb and 90% for Zn, though these are dependent on feed grade and mineralisation type of material fed to the plant.

All three circuits produce separate concentrates which are transferred to separate thickeners and storage tanks where the concentrate is filtered through a Larox filter press and stored in a concentrate shed for transport to customers offsite via trucks.

Mount Garnet Processing Plant in 2019