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Indonesia
Grasberg Block Cave Mine (Grasberg Complex)

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 Location:
56km NE from Timika, Indonesia

  Regional Office:
Plaza 89, Lt. 5 Jl. HR. Rasuna Said Kav. X-7 No. 6
Jakarta
Indonesia
12940
Phone  ...  Subscription required
Fax+62-21-2591945
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Fleet
  • Personnel
  • Filings & News

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Overview

StageProduction
Mine TypeUnderground
Commodities
  • Copper
  • Gold
  • Silver
Mining Method
  • Block caving
Processing
  • Gravity separation
  • Flotation
Mine Life2041
. As existing drawpoints mature and additional drawpoints are added, cave expansion is expected to accelerate production rates to an average of over 98,000 metric tons of ore per day in 2022 and 127,000 metric tons of ore per day in 2023 from five production blocks spanning 335,000 square meters. As of December 31, 2020, the Grasberg Block Cave had 229 open drawbells.


Owners

Source: p. 18
CompanyInterestOwnership
Freeport-McMoRan Inc. 48.76 % Indirect
PT Indonesia Asahan Aluminium (Persero) 51.24 % Indirect
PT Freeport Indonesia 100 % Direct
PT-FI is a limited liability company organized under the laws of the Republic of Indonesia. 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


Summary:

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.


Mining Methods

  • Block caving


Summary:

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. Monitoring data on cave propagation in the Grasberg Block Cave underground mine is providing confidence in growing production rates over time. As existing drawpoints mature and additional drawpoints are added, cave expansion is expected to accelerate production rates to an average of 30,000 metric tons of ore per day in 2020, over 60,000 metric tons of ore per day in 2021 and 130,000 metric tons of ore per day in 2023 from five production blocks spanning 335,000 square meters.

The Grasberg Block Cave fleet consists of approximately 460 pieces of mobile equipment. The primary mining equipment directly associated with production and development includes an available fleet of 52 LHD units and 35 haul trucks. Each production LHD unit typically carries approximately 11 metric tons of ore and transfer ore into 55 to 60 metric ton capacity haul trucks. In addition, the Grasberg Block Cave has a rail haulage system currently operating with 3 locomotives and 27 ore wagons that haul the ore to the first of the 3 planned gyratory crushers located underground via an automated rail system. Each ore wagon typically carries 30 metric tons.


Crushing and Grinding


Processing

  • Gravity separation
  • Flotation

Source: Subscription required

Summary:

The mill produces copper and gold concentrate from mined ore through a process to separate valuable minerals from the impurities covering them. The main steps in the process are crushing, grinding, flotation, and dewatering. Crushing and grinding transform ore size into fine sand in order to release particles containing copper and gold.

Flotation is a separation process to produce copper-gold concentrate. Concentrate slurry consisting of finely ground ore and water mixed with reagents is introduced into a series of mixing tanks called flotation cells, where air is pumped into the slurry.

The reagents used are lime, frothers and collectors. Frothers form stable bubbles that float to the surface of the flotation cell as froth. Collectors react with valuable metal sulfide mineral particle surfaces. rendering these surfaces hydrophobic. The hydrophobic sulfide mineral particles adhere to the air bubbles rising from the slurry zone into the froth floating on the surfac ........


Combined production numbers are reported under Grasberg Complex

Operational Metrics:

Metrics2019201820172016
Daily milling rate  ......  Subscription required4,000 t3,600 t2,700 t
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Reserves at December 31, 2019:

CategoryOreTypeTonnage CommodityGradeRecoverable Metal
Proven Mill / Sulphide 321 Mt Copper 1.11 %
Proven Mill / Sulphide 321 Mt Gold 0.86 g/t
Proven Mill / Sulphide 321 Mt Silver 3.88 g/t
Probable Mill / Sulphide 639 Mt Copper 0.89 %
Probable Mill / Sulphide 639 Mt Gold 0.66 g/t
Probable Mill / Sulphide 639 Mt Silver 3.56 g/t
Proven & Probable Mill / Sulphide 959 Mt Copper 0.97 % 17.2 B lbs
Proven & Probable Mill / Sulphide 959 Mt Gold 0.73 g/t 14.2 M oz
Proven & Probable Mill / Sulphide 959 Mt Silver 3.67 g/t 62.8 M oz


Heavy Mobile Equipment as of December 31, 2020:
HME TypeSizeQuantity
Load-Haul-Dump (LHD) 11 t 70
Truck (haul) 60 t 33

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Mar 12, 2021
....................... Subscription required ....................... Subscription required Subscription required Mar 12, 2021
....................... Subscription required ....................... Subscription required Subscription required Mar 12, 2021
....................... Subscription required ....................... Subscription required Subscription required Mar 12, 2021
....................... Subscription required ....................... Subscription required Subscription required Mar 12, 2021
Subscription required - Subscription is required.


Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2020
................................... Subscription required 2019
Form 10-K 2018
Form 10-K 2017
Corporate Presentation 2016
Other 2016
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Aerial view:

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