Mt Magnet, Murchison, Western Australia
The Mount Magnet (Mt Magnet) gold project is located in Western Australia and includes multiple underground and open-pit mines.
Discovered in 1891, the Mt Magnet project has historical production of six million ounces (Moz) of gold.
The project, which includes the historic Hill 50 gold mine, also comprises several exploration targets with the potential to host new discoveries.
The Hill 50 underground mining operation, the largest gold mine in the Mt Magnet district, was closed in 2007.
Ramelius Resources bought the gold project from Harmony Gold Australia in 2010 and restarted operations in 2011 with a reserve base of 545,000oz. The company achieved first gold pour at the project in March 2012.
Mt Magnet gold project location
The Mt Magnet gold project is a 225km² mining centre, located 600km north-east of Perth in Western Australia.
It is situated near the town of Mt Magnet in the Murchison Goldfield of Yilgarn Craton.
Geology and mineralisation of Mt Magnet gold project
The gold mine is hosted within the Meekatharra-Mt Magnet greenstone belt of the Murchison province. The greenstone belt stratigraphy is intruded by granitic rocks. The belt lithology includes a series of steeply dipping and inter-layered mafic and ultramafic intrusive and extrusive rocks, banded iron formations and felsic volcanic rocks.
The gold mineralisation is hosted by banded iron formations, and is associated with the replacement of magnetite by pyrite and pyrrhotite.
A considerable amount of gold mineralisation is also present in the felsic units of the Boogardie Basin, where the mineralisation exists as a stockwork type of sericite-silica-pyrite veining and modification within felsic porphyry units intruded into ultramafic flow arrangements.
Mt Magnet gold project reserves
The gold project is estimated to hold proven and probable reserves of 7.6Mt containing 360,000oz of gold (Au) at a grade of 1.5g/t Au, as of June 2019.
Mining at Mt Magnet gold project
The current mining operations include the Eridanus, Milky Way, Stellar West, and Vegas open pits, and the Hill 60 and Shannon underground mines. The key mining and exploration areas comprise the Galaxy mine area, Morning Star pit, Cosmos mine area, Water Tank hill, Hill 60, and Eridanus.
The project employs drill and blast, load and haul of ore and waste at the Blackmans, Titan and Brown Hill pits.
In June 2019, Ramelius announced a five-year life of mine plan, which considers producing in excess of 1Moz of gold from Mt Magnet and Edna May over a period of five years.
The exploration strategy for the Mt Magnet project under the plan includes drilling beneath new Eridanus open pit in the Cosmos mine area. A successful deep drilling programme extended the mine life at the Vivien Satellite mine to June 2021.
The company is also undertaking underground studies at the Galaxy area to evaluate options for converting approximately 470,000oz of existing mineral resources of the Saturn, Mars, Titan, and Hill 50 pits into the life of mine plan. Ramelius mined 2.33Mt of ore from the Mt Magnet project in 2019.
Processing at Mt Magnet gold project
Ore from the Mt Magnet project is processed at the Checkers Gold mill at the Hill 50 mine.
The Checkers Gold mill is an existing plant previously operated by Mt Magnet Gold and was decommissioned in December 2008. The facility was refurbished in November 2011.
The conventional semi-autogenous grinding (SAG) mill currently operates at a capacity of 1.9 to two million tonnes per annum (Mtpa) and is capable of operating at 2.4Mtpa.
It includes primary crushing, conveying, coarse ore storage, primary and secondary milling, gravity gold circuit with a gravity concentrator and an intensive cyanidation circuit. A seven-tank carbon-in-leach (CIL) circuit, 4t pressure Zadra elution circuit and electrowinning systems are used for gold recovery.
The mill produced a total of 12.72Mt of gold, graded at 1.77g/t for 672,938oz from production restart until June 2019.
The plant throughput was increased by 7% between 2018 and 2019 due to plant optimisation.
MACA is the mining contractor for open pits while Byrnecut Australia manages underground mining.
Watpac undertook open-cut operations at the Galaxy area of the Mt Magnet project.
GR Engineering was contracted to provide engineering, procurement, and construction (EPC) design, and project management services for the refurbishment of the Checker processing plant.