The Australian firm has received a revised mineral resource estimate for Tampakan, in which it holds a 37.5 percent interest, from project manager Xstrata Copper, a unit of global miner Xstrata Plc.

Based on the new information, Indophil said Tampakan was now believed to contain 15 million tonnes of copper and 17.9 million ounces of gold, up from the previous estimates of 13.9 million tonnes of copper and 16.2 million ounces of gold.

Indophil, partly owned by Philippine conglomerate San Miguel Corp, said in a statement the new estimate represents a tonnage increase of 18 percent over the October 2009 estimate.

The revised estimate comes as the Philippines' Department of Environment and Natural Resources (DENR) remains reluctant to issue an Environmental Compliance Certificate (ECC) for the project.

Sagittarius Mines Inc, Xstrata's Philippine unit, said on Jan. 13 it would ask the DENR to reconsider its decision denying its application for an ECC.

The ECC serves as a permit for Sagittarius to begin construction, but the DENR has said it could not issue the permit because of a provincial ban on open-pit mining.

Sagittarius is looking to begin Tampakan's commercial production by 2016 and will use open-pit mining to extract the minerals.

"The enhanced level of confidence provided in this upgraded resource estimate for Tampakan is encouraging," Indophil chief executive officer Richard Laufmann said.

"It is timely, and serves to restate the significance of this deposit to minerals development in the Philippines as the project partners work towards securing the range of approvals required to bring this important development to production," he said.