Las Lagunas Gold Tailings Project, Dominican Republic

Key Data

Las Lagunas Gold Tailings is a retreatment project involving the reprocessing of previously unrecovered gold and silver refractory tailings from the Pueblo Viejo mine.

The project is situated 100km north-west of Santo Domingo, the capital city of Dominican Republic, in the Caribbean. The project is 100% owned and operated by EnviroGold, which was renamed as Panterra Gold in September 2011.

The project is expected to recover a total 435,675oz of gold and 3.9Moz of silver throughout its 6.5 years of mine life production.

Las Lagunas Gold Tailings project history

"The project is situated 100km north-west of Santo Domingo, the capital city of Dominican Republic, in the Caribbean."

The Dominican State called for international tenders in 2001 for the evaluation and development of the 600m long Las Lagunas tailings dam. The public bids were received in October 2003. EnviroGold won the tender in March 2004.

The development agreement was signed in April 2004 to reprocess the sulphide tailings stockpiled at the dam through profit sharing with the government. The prefeasibility study was carried out in 2006, and the complete feasibility study report was prepared in 2007. The development of the Las Lagunas project began in 2009.

In January 2012, a 138kV national grid was connected to the processing plant through the 69kV Piedra Blanca-Hatillo line, which runs over the Las Lagunas project area. The process plant was commissioned in June 2012. As of January 2013, the tailings were being fed to the plant at up to 80% of design capacity.

Probable reserves at the Las Lagunas Gold Tailings project stand at 5.2 million tonnes (mt) graded at 3.67g/t Au and 37.6g/t Ag. The mine is estimated to contain 5.1mt of inferred resources, at an average grade of 3.76g/t Au and 38.62g/t Ag.

Production of gold from the Dominican Republic mine

The Las Lagunas project produced its first gold / silver doré in July 2012. It is expected to produce 83,700oz in 2013, 165,300oz in 2014, 176,800oz in 2015 and 178,300oz of Au in 2016. The production cost is anticipated to be $350 per oz Au.

Mining methods and processing at the Pueblo Viejo mine

Rosario Dominicana, a state-owned mining corporation, acquired the Pueblo Viejo mine in 1969. The run of mine (ROM) ore was extracted from the mine through open-pit operations between 1992 and 1999. The recalcitrant quality and metallurgical ramification of the ore resulted in poor gold recoveries. Poor recoveries and decreased gold prices led to the termination of operations of the Pueblo Viejo mine in July 1999.

"The Las Lagunas project produced its first gold / silver doré in July 2012."

In an effort to increase the quality of gold recovered from the Pueblo Viejo mine, the tailings were stockpiled in the Las Lagunas tailings dam. Trial mining was carried out at the Las Lagunas project in August 2011.

The tailings stockpiled at the dam are being processed using Xstrata's Albion oxidation and carbon-in-leach (CIL) techniques. They are retreated through the Albion oxidation process followed by the standard CIL method to produce high grade gold and silver dore bars.

The Albion oxidation processing plant can treat 800,000tpa of ore. It will produce around 85,000oz of Au equivalent during 6.5 years of mine life. The process involves grinding the ore in to small pieces and oxidising it in a leaching circuit at atmospheric pressure. The output of the Albion circuit is further refined in a cyanide leaching circuit to recover the highly graded gold and silver.

The Albion oxidation plant was supplied by Air Products and Chemicals.

Financing Panterra Gold's Las Lagunas project

EnviroGold signed an agreement with the Macquarie Bank to procure a $37.5m loan, with a guarantee to repay it within 18 months of commissioning of the Las Lagunas project. It also received a $7.5m advance loan against a three percent gold production royalty for the mine lifespan of 6.5 years. Funding began in October 2010.

The capital cost of the Las Lagunas tailings project is estimated at $82.7m, while the operating cost per tonne stands at $30.68.

Cerro De Maimon Copper and Gold Mine, Dominican Republic

Cerro De Maimon Copper and Gold Mine is located 70km northwest of Santo Domingo in the Monseñor Nouel Province in the Dominican Republic. The mine is 100% owned and operated by Australian company Perilya.