Indonesia was the world’s seventh largest gold producer in 2003, producing 163 t compared to 158 t in 2002. Over 70% of Indonesia’s production is generated as a by-product of copper mining at Grasberg and Batu Hijau, both of which reported higher production year on year.Grasberg, the world’s largest gold-producing mine, yielded 98 t in 2003, an 8% increase from 2002
The world class Grasberg mine is situated at Tembagapura, Irian Jaya. The mine has proven and probable reserves estimated at 2600 Mt grading at 1.13% copper, 1.05 g/t gold and 3.8 g/t silver. Reserve estimates have doubled since 1995. PT Freeport is Indonesia’s largest taxpayer and has paid an estimated $1.3 billion to the government since 1992.
The Hijau copper-gold mine is located on the island of Sumbawa at a cost of $1.9 billion. PT Newmont Nusa Tenggara (PTNNT) is the operator and represents a joint venture between Newmont Mining (45%), Sumitomo Corporation (35%) – collectively 80% and local partner PT Pukuafu Indah (20%). Reserves have been estimated at 1 000 Mt grading at 0.52% copper and 0.4 g/t gold, with an expected life of mine of 25 years.
Newmont holds an 80 percent interest in the Minahasa gold mine through PT Newmont Minahasa Raya. An Indonesian company, PT Tanjung Serapung, holds the remaining 20 percent. Other major gold and silver producers included of PT (KEM) Kelian Equatorial Minin’s Kelian Equatorial mine in East Kalimantan. The Mt Muro mine in Central Kalimantan is operated by Aurora Gold. Both the Kelian mine and the Minahasa Raya gold mine in North Sulawesi Province ceased mine production in 2003 and treated the remaining stockpiled ore. PT KEM managed to produce 14.58 t of gold and 10.78 t of silver, and PT Newmont Minahasa Raya’s plant produced 3.09 t.
PT Aneka Tambang’s Pongkor gold and silver mine near Bogor in west Java, produced 3.81 t of gold (and 25.4 t of silver) in 2002.
PT Antam’s Logam Mulia (LM) precious metals refinery in Jakarta recorded gold production in 2003 at 4,176 kg with sales at 4,829 kg. Logam Mulia, which also refines Antam’s gold bullion from the Pongkor gold mine, has an annual capacity of 75 t, but in 2003 it operated at only about 36% of capacity.
Antam’s Pongkor mine is an underground operation and possesses reserves of 6.63 Mt, sufficient for another 17 years and produced 4,497 t of gold and 29.85 t of silver in 2003. Antam’s Pongkor underground production came from three primary gold veins: Ciguha, Kubang Cicau and Ciurug. In 2002, Pongkor applied conventional cut-and-fill mining and treated 401,517 t of ore averaging 11.36 g/t Au and 141 g/t Ag to produce 3,813 kg of gold and 25,397 kg of silver. Output was 4% less than in 2001 because average grades were lower. Exploration is continuing and detailed work on the Gunung Handak vein, which has included 4,019 m of drilling, has added 1.0 Mt averaging 8.43 g/t Au and 121.24 g/t Ag to the indicated resource. Antam’s gold division also includes the country’s sole precious metals refinery, Logam Mulia (LM) in Jakarta. The refinery has an annual capacity of 75 t of gold and 275 t of silver.
Unless new gold and silver mines are developed and commissioned soon, which seems unlikely at the present time, production in the coming years will be largely restricted to the associated gold produced as a by-product in copper concentrates, mainly at Tembagapura and Batu Hijau, and to primary output at Pongkor, the sole remaining gold and silver mine.