Grasberg Minerals District
Description: The Grasberg minerals district includes open pit and underground mines.
Did You Know? PT Freeport Indonesia commenced mining operations in 1972 and in 1988 discovered the Grasberg mine. Today, after significant production, the Grasberg mining district contains one of the world’s largest recoverable copper reserve and the largest gold reserve.
We have several projects in progress in the Grasberg minerals district related to the development of large-scale, high-grade underground ore bodies. In aggregate, these underground ore bodies are expected to ramp up over several years to produce approximately 240,000 metric tons of ore per day (mtd) following the anticipated transition from the Grasberg open pit in 2017. Development of the Grasberg Block Cave and Deep Mill Level Zone (DMLZ) is advancing to enable the DMLZ to commence production in 2015 and the Grasberg Block Cave mine to commence production in 2017. In addition to the near-term development projects in progress, we also have a long-term underground mine development project for the Kucing Liar ore body, which lies on the southern flank of and underneath the southern portion of the Grasberg open pit.
Location: The remote highlands of the Sudirman Mountain Range in the province of Papua, Indonesia, which is on the western half of the island of New Guinea.
Ownership: 90.64% FCX (including 9.36% owned through our wholly owned subsidiary, PT Indocopper Investama); 9.36% the Government of Indonesia.
Mines, Processes and Facilities: The Grasberg minerals district currently has three mines in operation: the Grasberg open pit, the Deep Ore Zone (DOZ) underground mine and the Big Gossan underground mine.
Crushing and conveying systems are integral to the mine and provide the capacity to transport up to 250,000 mtd to the mill and 150,000 mtd of overburden to the overburden stockpiles.
Using ore passes and chutes, load-haul-dump units transfer ore into haul trucks. The trucks dump into two gyratory crushers and the ore is then conveyed to the surface stockpiles.
The success of the development of the DOZ, one of the world’s largest underground mines, provides confidence in the future development of PT Freeport Indonesia’s large-scale undeveloped underground ore bodies.
Big Gossan underground mine. The Big Gossan mine lies underground and adjacent to the current mill site. It is a tabular, near-vertical ore body. Production from the Big Gossan mine began in fourth-quarter 2010 and is designed to ramp up to 7,000 mtd in 2017.
The Big Gossan mine utilizes a blasthole stoping method with delayed paste backfill. Stopes of varying sizes are mined and the ore dropped down passes to a truck haulage level. Trucks are chute loaded and transport the ore to a jaw crusher. The crushed ore is then hoisted vertically to a level where it is loaded onto a conveyor belt. The belt carries the ore to one of the main underground conveyors where it is transferred and carried to the surface mill stockpile for processing.