Rosemont is an open pit gold mine located about 9km north-west of Garden Well gold mine in Western Australia. Rosemont is part of the Duketon Gold project, which also encompasses the Garden Well and Moolart Well gold mines.
The Rosemont deposit was discovered in 1980. Aurora Gold developed the deposit as a small shallow open pit. The ownership of the mine was transferred to Regis in 2006. Regis Resources currently fully owns the project and expects to produce 80,000oz of gold per annum.
The bankable feasibility study for the mine’s development was completed in July 2012 and the mining activities began in November 2012. The expected mine life of Rosemont is five years.
Rosemont mine geology
The Rosemont gold deposit is located within the Duketon Greenstone Belt. The deposit is hosted by deposits of quartz within a dolerite unit. The shear zone trends towards northwest and bends down towards east.
The mineralisation includes Archaean aged oxide and fresh rock gold. Gold mineralisation occurs 8m beneath the alluvial hardpan.
Rosemont mine reserves
The Rosemont open pit gold mine has reserves of 664,000oz of gold. The combined indicated and inferred resources have been estimated at 1.73 billion ounces of gold.
Gold mining and production
Regis Resources commenced pre-production mining at Rosemont in March 2013 and mined 478,000 billion cubic meters (bcm) of pre-strip waste material in March. It is expected to mine 10.5bcm of overburden pre-strip over the life of the project.
Gold production from the mine is expected to commence in 2013.
A crushing and grinding circuit with a capacity of 1.5 million tonnes per annum is being set up at the Rosemont gold project as part of the first stage of development. The ore slurry will be pumped to the Garden Well processing plant through a high-density polyethylene pipeline.
The slurry will be leached and processed to recover gold, at the carbon-in-leach (CIL) circuit of the Garden Well processing plant.
Mine expansion and infrastructure details
The second stage of development at Rosemont will include full development of the processing infrastructure by building a full-time processing plant alongside the CIL plant at Garden Well. The second stage is estimated to cost $50m. It will also involve installation of additional facilities such as the elution circuit, and the reagents storage and distribution system.
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The expansion is expected to increase the combined mill throughput of Garden Well and Rosemont mines from 6.5 million tonnes per annum (mtpa) to approximately 7mtpa to 8mtpa.
The plant’s design eliminates the need for an additional tailings storage facility (TSF) at Rosemont, as it is in close proximity to the Garden Well mine.
A 100-member accommodation unit established at the Garden Well camp is being used to accommodate the Rosemont mine employees.
The project will get power supply from the Garden Well power plant. Regis Resources has installed four Cummins KTA50-G3 diesel engines to increase the power plant’s capacity from 12MW to 16MW.
The proximity will help in cutting the cost of operations and overheads through common use of the infrastructure.
Construction details and other facilities at the Rosemont gold project
Regis Resources commenced the construction of the development works at Rosemont gold mine in September 2012. Construction of the crushing and grinding unit began in March 2013 and is expected to be completed in September 2013 marking the completion of the first-stage works.
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The work includes construction of offices, site earth-works, concrete works for the mill, and crusher foundations. It also includes setting up of mill components and crushing circuit equipment.
The Rosemont project will also provide for the storage of 165,000 litres of diesel in addition to 1.5 million litres stored at Garden Well. Provision is also made to store reagents such as hydrocarbons, liquid petroleum gas, and activated carbon.
Financing and contractors
Regis Resources is utilising its operating cash reserves for financing of the Rosemont gold project.
EGRM Consulting conducted the resource estimation study for Rosemont gold mine.
Mining And Civil Australia (MACA) was awarded the contract for providing mining services at Rosemont mine. The scope of services includes drilling and blasting, loading, and hauling. The five-year mining contract is valued at $220m.