Market Survey on Copper - Indian Bureau of Mines

The Dalam Diatreme (DD) forms the first intrusive stage, being highly
fragmental and characterised by clasts and a matrix of dioritic composition.“The open
pit mine is a high-volume low-cost operation, producing more than 67 million tonnes
of ore.”Mineralisation is largely disseminated and chalcopyrite dominant, having
average grades of 1.2% copper and 0.5 g/t gold.
The second intrusive stage, the Main Grasberg Stock (MG), is composed of
non-fragmental, porphyritic monzodiorites, forming a quartz-magnetite dilational
stockwork with veinlet controlled copper-gold mineralisation. This is a high-grade
resource, with averages of 1.5% copper and 2 g/t gold.
There is also a third intrusive stage, associated with the South Kali Dykes,
which was the final intrusion and the most weakly mineralised.
Mining
The workings comprise an open pit mine, an underground mine and four
concentrators. The open pit mine – which forms a mile-wide crater at the surface – is
a high-volume low-cost operation, producing more than 67 million tonnes of ore and
providing over 75% of the mill feed in 2006.
Designed to be fully mechanised, using 6.2m 3 Caterpillar R1700 load-hauldump
vehicles (LHDs) at the extraction level with a truck haulage level to the
gyratory crusher, the Deep Ore Zone (DOZ) block cave mine is one of the largest
underground operations in the world.
After 2004, when the DOZ mine averaged 43,600 tonnes/day a second
underground crusher and additional ventilation were installed to increase daily
capacity to 50,000 tonnes.Ore from both operations is transported by conveyor to
centralized mine facilities, feeding a combined daily average total of some 225,000t
of ore to the mill and 135,000t to the stockpiles.
Production equipment includes 30m 3 –42m 3 buckets, a 170-strong fleet of 70t–
330t haul trucks, together with 65 dozers and graders, with radar, GPS and robotics
used in the mine’s state-of-the-art slope-monitoring system.
Processing
Ore undergoes primary crushing at the mine, before being delivered by ore
passes to the mill complex for further crushing, grinding and flotation. Grasberg’s
milling and concentrating complex is the largest in the world, with four crushers and
two giant semi-autogenous grinding units processing a daily average of 240,000t of
ore.“This is a high-grade resource, with averages of 1.5% copper and 2 g/t gold.”
A flotation reagent is used to separate concentrate from the ore. Slurry
containing 60-40 copper concentrate is drawn along three pipelines to the seaport of
Amamapare, over 70 miles away, where it is dewatered. Once filtered and dried, the
concentrate – containing copper, gold and silver – is shipped to smelters around the
world.
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