Description: Grasberg is a world-class mining complex in Indonesia, where Freeport-McMoRan Copper & Gold is engaged in exploration and development, mining and milling of ore containing copper, gold and silver.
Did You Know? PT Freeport Indonesia commenced mining operations at this site in 1972 and in 1988 discovered the Grasberg mine. Today, after significant production, the Grasberg mining district contains the world’s largest recoverable copper reserve and the largest gold reserve.
Location: Papua, Indonesia
Ownership: We own 90.64% of PT Freeport Indonesia, the principal operating subsidiary in Indonesia, including 9.36% owned through its wholly owned subsidiary, PT Indocopper Investama. The Government of Indonesia owns the remaining 9.36% of PT Freeport Indonesia.
FCX operates under an agreement with the Government of Indonesia, which allows us to conduct exploration, mining and production activities in a 24,700-acre area (Block A). We also conduct exploration activities in an approximate 500,000-acre area (Block B). All of our proven and probable mineral reserves and current mining operations are located in Block A.
Mines, Processes and Facilities: Two mines are currently in operation: the Grasberg open pit and the Deep Ore Zone (DOZ) underground block cave.
Grasberg. We began open-pit mining of the Grasberg ore body in 1990. Open-pit operations are expected to continue through 2015, at which time the Grasberg underground mining operations are scheduled to begin. Production is currently at the 3,295- to 4,285-meter elevation level and totaled 49.0 million metric tons of ore in 2008 and 57.5 million metric tons of ore in 2007, which provided 67 percent of our 2008 mill feed and 75 percent of our 2007 mill feed. Remaining mill feed comes from our DOZ mine.
DOZ. The DOZ ore body lies vertically below the now depleted Intermediate Ore Zone. We began production from the DOZ ore body in 1989 using open stope mining methods, but we suspended production in 1991 in favor of production from the Grasberg deposit. Production resumed in September 2000 using the block-cave method. Production is at the 3,110-meter elevation level and totaled 23.1 million metric tons of ore in 2008 and 19.5 million metric tons in 2007.
During 2008, we completed over 16,000 meters of development drifting in support of the block-cave mining method for the DOZ mine. Further expansion of the DOZ operation to 80,000 metric tons of ore per day is under way with completion targeted by 2010. The success of the development of the DOZ mine, 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.
Development Projects. In addition to the Grasberg open pit, four other ore bodies (the Grasberg block cave, Big Gossan, Deep MLZ, and Kucing Liar) are located in Block A. We have several projects in progress in the Grasberg minerals district, including developing the large scale, high-grade underground ore bodies located beneath and adjacent to the Grasberg open pit. These ore bodies are included in our proven and probable recoverable reserves.
Ore Bodies: Our ore bodies are located within and around two main igneous intrusions, the Grasberg monzodiorite and the Ertsberg diorite. The host rocks of these ore bodies include both carbonate and clastic rocks that form the ridge crests and upper flanks of the Sudirman Range, and the igneous rocks of monzonitic to dioritic composition that intrude them. The igneous-hosted ore bodies (the Grasberg open pit and block cave, and the DOZ block cave) occur as vein stockworks and disseminations of copper sulphides, dominated by chalcopyrite and, to a much lesser extent, bornite. The sedimentary-rock hosted ore bodies occur as “magnetite-rich, calcium/magnesian skarn” replacements, whose location and orientation are strongly influenced by major faults and by the chemistry of the carbonate rocks along the margins of the intrusions.
The copper mineralization in these skarn deposits is also dominated by chalcopyrite, but higher bornite concentrations are common. Moreover, gold occurs in significant concentrations in all of the district’s ore bodies, though rarely visible to the naked eye. These gold concentrations usually occur as inclusions within the copper sulphide minerals, though, in some deposits, these concentrations can also be strongly associated with pyrite.
The Grasberg complex shown below illustrates the layout of the current 2.7 billion metric ton Grasberg/Ertsberg minerals district reserves. The western side of the district is dominated by the Grasberg, with its massive open pit (final design shown) and block cave mineable reserves, and the Kucing Liar and Big Gossan ore bodies. The eastern side of the district is dominated by the Ertsberg East ore bodies, the DOZ and the Deep MLZ. The underground production and exploration access to these ore bodies is shown.
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