Description

The Grasberg minerals district includes open-pit and underground mines.

Did you know?

PT Freeport Indonesia (PTFI) 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.

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.

Processes and facilities

The Grasberg minerals district includes the following underground mines that are being operated; the Grasberg Block Cave, the Deep Mill Level Zone (DMLZ) and Big Gossan. Production from these underground mines is expected to continue through 2041 and an extension of PTFI’s operating rights beyond 2041 would extend the lives of these mines. PTFI also has several projects in progress in the Grasberg minerals district related to the development of the large-scale, long-lived, high-grade underground ore bodies located beneath and nearby the Grasberg open pit. In aggregate, these underground ore bodies are expected to produce large-scale quantities of copper and gold.

Grasberg Block Cave. The Grasberg Block Cave ore body is the same ore body historically mined from the surface in the Grasberg open pit. Undercutting, drawbell construction and ore extraction activities in the Grasberg Block Cave underground mine continue to track expectations.

DMLZ underground mine. The DMLZ ore body lies below the depleted Deep Ore Zone (DOZ) underground mine at the 2,590-meter elevation and represents the downward continuation of mineralization in the Ertsberg East Skarn system and neighboring Ertsberg porphyry. Hydraulic fracturing operations have been effective in managing rock stresses and pre-conditioning the cave following mining-induced seismic activity experienced from time to time.

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. The 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 via a two-skip production shaft to a level where it is loaded onto a conveyor belt. The belt carries the ore to one of the main underground conveyors where the ore is transferred and conveyed to the surface stockpiles for processing.

Kucing Liar Underground Mine. PTFI commenced long-term mine development activities for its Kucing Liar deposit in October 2021, which is expected to produce over 7 billion pounds of copper and 6 million ounces of gold between 2029 and the end of 2041, and an extension of PTFI’s operating rights beyond 2041 would extend the life of the project. The Kucing Liar underground deposit lies on the southern flank of and underneath the southern portion of the Grasberg open pit at the 2,605-meter elevation level. Development activities are expected to continue over an approximate 10-year timeframe. At full operating rates, annual production from Kucing Liar is expected to approximate 560 million pounds of copper and 520 thousand ounces of gold, providing PTFI with sustained long-term, large-scale and low-cost production.