Name: Gosowong mine.
Location: The Godoswong mine is located on the island of Halmahera, in North Maluku province, Indonesia.
Controlling Company: The mine is owned and operated by PT Nusa Halmahera Minerals, an Indonesian company owned by Newcrest Mining (75%) and PT Aneka Tambang or Antam (25%).
Brief Description: Gosowong currently encompasses the Kencana and Toguraci underground mines.
Brief History: Newcrest formed a joint venture with Antam in 1994 to explore for gold on Halmahera, with economic gold grades discovered at Gosowong in May 1994.
The Gosowong contract of work was granted by the Indonesian government in 1997, with engineering, feasibility and environmental-impact studies completed thereafter.
First gold doré was poured at Gosowong in July 1999.
Products: Gold and silver.
Geology/Mineralisation: All economic mineralisation at Gosowong is of low sulphidation epithermal-type, occurring as mineralised fault systems resulting from high-temperature gold- and silver-bearing hydrothermal fluids. The ore shoots are narrow and level, although irregular and complex in local detail. The deposits are relatively moderate to low in dip, averaging at about 40° to 50° in the Kencana to Gosowong structural corridor, and subvertical in the Toguraci corridor. Silver to gold ratio in the ore is estimated at 1:1.
Reserves: Proven and probable reserves were estimated at 1.8-million dry tonnes, grading 1.3 g/t of gold and 19 g/t of silver.
Resources: Mineral resources were estimated at 4.1-million dry tonnes, grading 1.2 g/t of gold and 20 g/t of silver as at December 31, 2015.
Mining Method: Openpit and underground mining methods have been used at Gosowong, with current mining from underground operations at Kencana (K1, K2 and K-Link) and at Toguraci (Midas, Damar and Yahut). The Kencana under- ground mine uses predominantly underhand cut-and-fill, with some long hole stoping, while the Toguraci underground mine also uses long hole stoping and overhand cut-and-fill.
Major Infrastructure and Equipment: The processing plant at Gosowong, which has a capacity of up to 800 000 t/y, comprises a primary jaw crusher, a semiautogenous and ball mill circuit and a Vertimill circuit. The ore undergoes a con- ventional cyanide leaching process.
Gold and silver are recovered from the cyanide solution using the Merrill-Crowe zinc precipitation process and are smelted to produce gold and silver doré. The gold doré is refined at Logam Mulia, which is owned by Newcrest’s joint venture partner Antam.
Prospects: On February 9, Newcrest suffered what it called a serious “geotechnical event” at the Kencana underground operation, which resulted in several mining levels being damaged and one of the mine’s employees being trapped about 300 m underground. The employee was rescued on February 16, with all mining and processing operations remaining suspended at the time of going to print until the cause of the accident was established.
Contact: Corporate affairs.
Contact Details:
Newcrest Mining,
tel +61 3 9522 5333,
fax +61 3 9525 2996,
email corporateaffairs@newcrest.com.au, and
website http://www.newcrest.com.au.