Troy’s Casposo Gold-Silver Project Goes Into Production

Troy Resources NL (Troy), duallisted on the Australian and Toronto Stock Exchanges (code: TRY), is a junior gold producer with operations at Sandstone in Western Australia and the Andorinhas Gold Mine in the Para State of north-central Brazil.

Troy’s latest low-cost operation is the recently constructed and commissioned Casposo Gold-Silver Project. This project is located within the San Juan Province in the north-west of Argentina, approximately 120 kilometres from the town of San Juan. The project comprises a 400,000 tonne per annum Merrill Crowe gold-silver processing plant with indicated and inferred resources totalling 0.44 Moz gold and 17.5 Moz silver and total production of 0.32 Moz gold and 9.04 Moz silver predicted over the six year mine life.

Silver and gold-bearing ore from the Casposo Gold-Silver Project contains a complex mix of gold, silver, electrum and silver sulphides. Casposo is a typical low sulphidation epithermal style gold–silver deposit in which mineralisation is hosted within rhyolite-andesite flows and breccias. Veins are typically banded quartz–chalcedony colloform-crustiform banded with quartz-carbonate infill. Mineralisation is associated with an assemblage consisting of quartz, chalcedony, adularia, calcite, illite, sericite and trace sulphides.

The final process flowsheet selected for the project was based on the traditional Merrill Crowe process. Merrill Crowe was used because of the very high silver grades of the ore (202 g/t – Indicated Resource Statement). The process is based upon the following main stages following the comminution circuit:

• Cyanide leaching;

• Solid-liquid separation;

• Pregnant solution clarification and de-aeration,

• Cementation of precious metals using zinc powder.

The plant was designed to minimize capital cost and technical risk, while maximizing the plant’s operability and gold/silver recovery.

The front end of the plant utilized equipment sourced from the Cobar Plant, which was previously obtained by Troy and stored in New South Wales. Where required, other components were sourced from Australia, Canada, Germany and the United States to complete the plant design. The use of the second-hand plant and equipment changed the project from being nonprofitable (capital cost US$86M) when owned by another company, to being viable with Troy (capital cost US$41.5M).

The engineering design was completed by Mineral Engineering Technical Services Pty Ltd. (METS) during 2009 and 2010, with the plant being commissioned with the assistance of METS during the fourth quarter of the year. The first production of gold and silver doré was completed on the 19th of November 2010 and the ramp-up to the full production rate will continue into 2011 with the installation of the plant’s automated process control.

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