The open-pit method is used in mining the Grasberg ore body, as this method is suitable for Grasberg, where the ore body occurs near the highland surface (Grasberg).

Almost the entire open-pit mining process consists of the stages of drilling, blasting, sorting, hauling, and crushing of ore. Another crucial activity is maintaining slope stability and revegetating (reclaiming) land no longer used for mining with native plants.

At the Grasberg open-pit mine the primary equipment used are drills, shovels, and large trucks to extract materials. Materials referred to are classified as ore and overburden, depending on their economic value. Shovels dig up material from different areas in the open-pit mine, and load the material onto trucks to be hauled out of the open-pit mining area.

PT Freeport Indonesia employees at the Grasberg open-pit mine

Ore is placed into crushing machines and conveyed to an ore mill for processing. Overburden is placed in designated locations, or in OHS crushers on the HEAT road for placement in Lower Wanagon next to stackers.

The main facilities located near the open-pit mine include maintenance workshops, a limestone quarry and treatment plant, and other supporting facilities and offices.

Development

The Grasberg open-pit mine is developed through multiple pushbacks simultaneously. Each pushback is part of a long-term development plan to mine the deposit. Some pushbacks require years to remove overburden before ore is exposed.

At Grasberg, the current primary ore-producing pushback is the 7S area. The schedule for high-grade mineral extraction is based on overburden removal prior to ore extraction. When work on one pushback is completed, overburden in the next pushback is stripped before ore is extracted. The overall open-pit mine process is scheduled in order to net present value of the mineral resource.

Overburden Placement

Overburden is rock material having no or little economic value covering a deposit. Throughout the Grasberg mining period, 3.4 billion metric tons of overburden will have been stripped to expose 1.4 billion metric tons of ore with economic value. Overburden consists of different natural rocks, including limestone. Overburden is placed in areas allowing continual development of the open-pit mine in the closest proximity possible for resource efficiency purposes.

The primary overburden placement area is on the Carstenz grass field and in the Wanagon area to the west and north. Overburden is hauled to dumps on trucks. In several placement areas such as Lower Wanagon, haul trucks first unload overburden into crushing machines, and the crushed overburden is then removed to a stacker for stockpiling in Lower Wanagon. Over the life of the open-pit mine, the stripping ratio (of overburden removed to ore) is 2.5. Between 1990 and 2006 it was 2.8, but from now to the end of the open-pit lifetime, it is expected to be 2.2. Upon completion of the pit, the overburden areas will be revegetated.

We are currently using 17 large shovels and 148 haul trucks to mine the Grasberg surface.

Operational Advantages

Enhancement programs underway are focused on driving value at our Grasberg mine. Initial efforts have determined productivity targets from the fleets of trucks and shovels. The focus of such initiatives was to enhance productivity of trucks and shovels, drilling and blasting, scorecard operators, site maintenance, inventory reduction, work scheduling, field supervisor training, and light vehicle use.

Enhancement programs underway are focused on driving value at our Grasberg mine. Initial efforts have determined productivity targets from the fleets of trucks and shovels. The focus of such initiatives was to enhance productivity of trucks and shovels, drilling and blasting, scorecard operators, site maintenance, inventory reduction, work scheduling, field supervisor training, and light vehicle use.

Golden Horseshoe
Sequencing in "golden horseshoe" mining in the Grasberg pit results in varied metals production from time to time.

We continue to perform longer-term analysis to optimize design of Grasberg open-pit mining that would affect Grasberg underground block cave development timing. Our previous plan included transition from Grasberg open-pit mining to Grasberg block caving by 2015. PTFI expects to complete the current study on a longer-term schedule before the end of 2006.

We have two trams operating from the mill to the pit. The first was built in 1971, and is now used for transporting equipment, materials and passengers, in addition to conveying ore from the mine to the mill. At the time it was built, the tram was the first aerial tram with the longest span in the world. The second tram was built in 1989. Following construction of an ore pass in 1989, trams are no longer used for conveying or to the mill.

Mining Equipment
TypeSize#
Shovel
O&K RH20030m38
Bucyrus 49542m34
P&H 410042m34
P&H 280034m36
Haul Truck
CAT 785135mt11
CAT 793220mt98
Komatsu 930E290mt27
CAT 797320mt12
Alat Pendukung
Kami juga menggunakan CAT 777 untuk bongkar muat dan kegiatan pendukung lainnya
Kami menggunakan beberapa alat bergerak untuk kegiatan pendukung; loader, dozer, excavator, grader, truk servis, crane, drill, d

Primary Associates in Grasberg

Drilltech/Sandvik
for blasthole drilling and drill maintenance.

Trakindo CAT
truck maintenance.

Benches 
Bench height is 15 meters with a face angle of 65o. Gradients range from 34o to 48o, depending on various geological considerations

Drilling and Blasting
The pattern commonly used is 10 x 10 x 17 meters.
ANFO is the explosive used.

Rainfall 
Averages 10mm/day (145 inches/year).