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The Hera-Nymagee underground mine is located approximately 100km south-east of Cobar, central New South Wales, Australia. The project involves the development of Hera gold base metal deposit and the Nymagee copper deposit.
The Hera deposit commenced first production in September 2014. The project became fully operational in April 2015, marking the start of commercial production. It is estimated to produce 50,000oz of gold a year and expected to have a mine life of 7.3 years.
The deposit was first discovered in 2001. Aurelia Metals (formerly YTC Resources) acquired the Hera deposit from CBH Resources in 2009. The NSW state government approved the mine’s development in August 2012.
Aurelia Metals owns 95% of the Nymagee copper deposit while Minmetals Resources holds the remaining 5%.
Hera-Nymagee geology and mineralisation
The Hera-Nymagee corridor is located in the eastern region of the Cobar Basin. It is a part of the Lachlan Orogen division and contains polymetallic ore bodies. It consists of shelf and turbiditic sedimentary rock sequences.
Hera is a superior-quality, lead-gold-zinc-silver deposit. Its decline is extended up to 674m-deep. It contains massive quartz rocks with liquid-rich fluid inclusions. High-grade copper sulphide mineralisation is found within the deposits.
Cubanite deposits are also found in the chalcopyrite sections of the Nymagee deposit. The mineralisation remains open at the north section and at depth.
Hera-Nymagee mine reserves
The Hera deposit has approximately 390,000oz of gold resources, in addition to 3.46 million ounces (Moz) of silver, 113,000t of lead and 148,000t of zinc. The combined measured, indicated and inferred resources have been estimated at 3.2 million tonnes (Mt).
The resources at Nymagee copper deposit have been estimated at 8.1Mt.
Mining and ore processing at Hera-Nymagee
The longhole, open-stoping method is used to mine the Hera deposit. Cemented rock fill (CRF) sill pillars are placed to divide the mine into discreet stoping areas.
The processing plant is a three-stage crushing circuit unit capable of grinding up to 250 micron. Gravity gold recovery circuit is used to extract 60% gold and 8% silver.
The Merrill Crowe method is applied for the processing of the Au-Ag components, and the bulk sulphide flotation method is used for base metal extraction.
Hera-Nymagee mine development
The Hera-Nymagee mine is being developed in two stages. Establishment of an underground mine and a processing plant at the Hera deposit are undertaken in the first stage. The plant produces gold and silver doré bars and lead-zinc concentrate.
The second stage involves the integration of the Nymagee copper deposit using the Stage 1 infrastructure. The Hera gold processing plant is flexibly designed, so it can be turned into a processing unit for Nymagee copper ore in Stage 2.
Infrastructure facilities at Hera-Nymagee mine
The infrastructure at Hera-Nymagee project includes the construction of a diesel-generator power station and a tailings storage facility. Workers are accommodated at the 80-person accommodation village.
The major construction works at Hera-Nymagee include the establishment of the Hera decline portal, a concrete batch plant, water supply system and sewage treatment plant.
Financing for the Hera-Nymagee mine
Glencore financed $155m for the Hera-Nymagee project. The financing was made in the form of debt and a converting note facility while fully funding the project.
The funding includes a $2.95m placement in Aurelia Metals shares.
Contractors involved with the Hera-Nymagee mine development
The engineering, procurement and construction contract for providing the processing plant was awarded to Gekko Systems.
The mining contract at Hera deposit was awarded to Pybar. According to the seven-year contract, Pybar performs the drill and blast, shotcreting, cable bolting, trucking and production works.
Ausco Modular was awarded the contract for building the accommodation village at the Hera-Nymagee project.
Optiro Mining Consultants conducted the definitive feasibility and mining studies. The geotechnical study for the Hera-Nymagee project was conducted by Coffey Mining.
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