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| Gold mine Batu Hijau is located on the Sumbawa island in the province of West Nusa Tenggara, Indonesian country |
Gold processing in the Batu Hijau mine, through several process stages. Ranging from drilling and blasting rock mineral, up to hauling rock material into the processing plant area
Gold mine Batu Hijau is located on the Sumbawa island in the province of West Nusa Tenggara, Indonesian country. The mine is the result of a ten-year exploration and construction program based on a 1999 discovery of the porphyry copper deposit. Production began in 2000.
The Batu Hijau mine is an open pit copper-gold mine operated and the project is held by Newmont Mining Corporation's subsidiary company PT Newmont Nusa Tenggara (PT Newmont), a company owned by Newmont Indonesia (US, 35.44%); Nusa Tenggara Mining Corporation (Japan, 27.56%), PT Pukuafu Indah (Indonesia, 20%) and PT Multi Daerah Bersaing (Indonesia, 17%).
Mineral Deposit In Batu Hijau Mine
Batu Hijau is a porphyry copper deposit containing small amounts of gold and silver, which is common for a copper deposit in southeast Asia.
Porphyries at Batu hijau mine are overwhelmingly hosted by composite stocks of diorite to quartz-diorite and, to a much lesser degree, more felsic compositions such as tonalite and monzogranite.
Copper sulphides such as chalcopyrite and bornite are frequently associated with the gold component of these deposits.
A porphyry deposit is one in which the valuable metals are not immediately available and require processing since they are mixed with rocks and minerals that are not economical to process.
The deposits tend to be characterised by a strong correlation between the distribution of copper sulphides (chalcopyrite and bornite) and gold as the native metal in addition to having a notably higher magnetite content.
Gold typically occurs as minute (<10-15 micron) inclusions in the copper sulphides. Porphyry deposits also are known to have lower grades.
Gold Processing Newmont At Batu Hijau Mine
Mining process begins with drilling and blasting in the Batu hijau mine. In the drill-and-blast method, a drilling equipment is used to drill a predetermined pattern of holes to a selected depth in the rock face path.
The drilled holes are then filled with explosives. The blasts loosen and break the rocks into sizes typically less than 25 cm in diameter.
Ore is removed from the mining face using P&H 4100 electric shovels and loaded into Caterpillar 793C haul trucks. the ore is loaded onto and hauled by 240-tonne capacity haul trucks to two primary crushers.
Each haul truck can move a payload 220 t (240 short tons) of ore. The trucks haul ore from the shovel to primary crushers.
In the primary crushers, the ore size is reduced to an average diameter of less than 15 cm. Ore is then hauled to the mineral recovery process plant while the subgrade is hauled to sub-grade stockpiles for possible future processing.
Crushed ore is sent by a conveyor 1.8 m (6 ft) wide and 6.8 km (4.2 mi) long to the mill.
The rock is mixed with seawater and ground using two Semi Autogenous Grinding (SAG) mills and four Ball Mills to create a slurry. Once milled it is sent through a flotation circuit which produces a concentrate with a grade of 32% copper and 19.9g/t gold.
The mill realizes a copper recovery of 89%. The concentrate is thickened into slurry and piped 17.6 km (10.9 mi) to the port at Benete where water is removed from the slurry, in large tanks and continuously stirred to avoid settling
The resulting liquid concentrate is transferred into counter-current decantation tanks where seawater is removed and the concentrate is thickened by running fresh water in the opposite direction. The fresh water displaces the seawater and the concentrate settles to the bottom of the tank.
The slurry is then pumped to another set of cyclones and then to Fotation tanks where the valuable minerals, such as copper, are recovered.
It is then filtered to remove 91 percent of the water using air pressure and takes the form of a fine powder, which is stored in a large,
covered building until it ships. The concentrate is finally shipped to a number of smelters in the country, including PT Smelting in Gresik, and overseas (Japan, South Korea, India, Europe) where it is smelted down to separate and to recover the valuable metals, mainly copper, gold and silver.
The tailings from the operation flow by gravity from the process plant to the ocean where they are deposited 3km from the coast at a depth of about 108m. From there, the tailings, which are non-toxic and non-hazardous, migrate towards the Java Trench and are ultimately deposited at depths in excess of 4,000m.
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