Indonesia

Grasberg Block Cave Mine

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Categories

Overview

Mine TypeUnderground
Commodities
  • Copper
  • Gold
  • Silver
Mining Method
  • Block caving
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ShapshotThe Grasberg Block Cave mine is a part of Grasberg minerals district.

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. As of beginning 2024 the Grasberg Block Cave underground mine had 425 open drawbells.
Related AssetGrasberg Complex

Owners

SourceSource
CompanyInterestOwnership
Freeport-McMoRan Inc. 48.76 % Indirect
PT Indonesia Asahan Aluminium (Persero) 51.24 % Indirect
PT Freeport Indonesia (operator) 100 % Direct
PT Freeport Indonesia (PT-FI) is a limited liability company organized under the laws of the Republic of Indonesia. PT-FI operates the mines in the Grasberg minerals district.

Freeport-McMoRan have a 48.76 percent share ownership in PT-FI and the remaining 51.24 percent share ownership is held by PT Indonesia Asahan Aluminium (an Indonesian state-owned enterprise).

Deposit type

  • Skarn
  • Vein / narrow vein
  • Breccia pipe / Stockwork

Summary:

The Grasberg minerals district is situated on the crest of the Sudirman Mountain Range at elevations over 2,500 meters with the highest peak, Puncak Jaya at 4,884 meters. Ore deposits in the Grasberg minerals district have economic copper, gold, and silver mineralization in porphyries and skarns. The primary sulfide mineralization is chalcopyrite, with lesser bornite, chalcocite, and covellite. Gold concentrations usually occur as inclusions within the copper sulfide minerals although in some parts of deposits gold can also be strongly associated with pyrite.

There are five major ore bodies all within the center of the Grasberg minerals district:
• Grasberg Intrusive Complex (GIC) includes the GBC and the depleted GRS_OP.
• EESS includes DMLZ and depleted GBT, IOZ, DOZ block caves.
• BG.
• KL (development stage mineral reserve).
• Dom (classified as mineral resource).

In Grasberg Block Cave (GBC) Mine area, anhydrite-gypsum and sulfur mineral distribution can be traced in Grasberg Intrusive Complex (GIC), skarn, and Heavy Sulphide Zone (HSZ).

GIC and Skarn contain abundant of anhydritegypsum as product of alteration. Potassic alteration in GIC are characterized by anhydrite appearance within the rock or as intense stockwork veins associate with quartz-pyritechalcopyrite. In the skarn, anhydrite mineral appear as dominant alteration mineral especially if the skarn occurred between contact of igneous rock and Waripi Dolomite with enough temperature to form anhydrite. Not only within the rock anhydrite also as vein and fill the fracture associated with suphide mineral pyritechalcopyrite. This anhydrite add by water become gypsum as result. Gypsum is easier to dissolve in water so can caused high sulfate content in water. Both potassic alteration GIC and skarn contain gypsum associated with 3-5% pyrite and 1-2% chalcopyrite content as disseminated. Even locally up to 5-10% pyrite and 3% chalcopyrite also minor sphalerite as replacement sulphide alteration or intense patchy.

Heavy Sulphide Zone in GBC area is characterized by more than 20% pyrite content and strong-pervasive replacement sulphide alteration. Locally pyrite content could up to more than 50%. The dominant sulphide content comprises of pyrite-chalcopyrite-pyrhotitesphalerite and easily oxidized if contact with ground water especially for pyrite.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

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Processing

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Production

Combined production numbers are reported under Grasberg Complex

Operational metrics

Metrics20232022202120202019201820172016
Daily ore mining rate  ....  Subscribe  ....  Subscribe  ....  Subscribe
Daily milling rate  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe8,600 t4,000 t3,600 t2,700 t

Production Costs

Commodity production costs have not been reported.

Heavy Mobile Equipment

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Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Feb 21, 2024
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Aerial view:

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