Intrepid Mines has reported the results of a preliminary economic assessment (PEA) for a potential open-pit, heap-leach gold project on the oxide resource at the Tujuh Bukit project in the far southeast of the island of Java, Indonesia.

Intrepid, an Australian company based in Brisbane, has an 80% interest in the pro-ject; PT Indo Multi Niaga, an Indonesian company, holds the remainder. Kappes Cassiday prepared the PEA based on column leach and other metallurgical tests performed at its laboratory in Reno, Nevada, USA. The PEA considered only the near-surface oxide resource at Tujuh Bukit and not the far-larger underlying porphyry resources.

The PEA postulates production of 143,000 oz/y of gold over a nine-year mine life at a cash cost of $376/oz, net of silver credits. Mine production would total 57 million mt grading 0.83 g/mt gold and 23 g/mt silver over the life of the project. Mill feed would average 20,000 mt/d. Preproduction capital cost, assuming contract mining, is estimated at $204 million. Processing would include a conventional cyanide heap leach followed by Merrill Crowe precipitation and smelting to produce gold-silver doré on site.

Intrepid’s board of directors has approved work necessary to support a prefeasibility study, including in-fill drilling, additional metallurgical test work, engineering design and financing evaluation. The forestry approval process will be conducted in parallel with this work.