July 13, 2005

YANACOCHA GOLD MILL

July 13, 2005

PROJECT IS STRATEGICALLY IMPORTANT TOYANACOHA OPERATION

Project is economically attractive.

Ores are becoming more complex. GoldMill is an alternative process to treat thesematerials.

Gold Mill Facility provides the basefacilities and skills for future complex oresat Yanacocha.

July 13, 2005

RESOURCE SUMMARY FOR GOLD MILLTotal Tonnes– 41.5 million tonnes

Average Ore Grade– Au 3.92 g/t Ag 24.37 g/t

Contained Ounces– Au 5.2 Moz Ag 32.5 Moz

Recoverable Ounces– Au 4.15 Moz Ag 14.2 Moz

Deep Transition Reserves Ounces (Contained)– Au 980 Koz

July 13, 2005

PROCESS

Stockpile

Agglom erationPrimary Crusher

Counter CurrentDecantation (CCD)

Acidification, Volatilization,Re-adsorption (AVR)

Sulfidization, Acidification,Recirculation & Thickening (SART)

Leach Circuit24 Hrs

ElectricalSubstationArea

Grindingcircuit

Video

July 13, 2005

GOLD MILL PROCESS FLOWSHEET

Crusher Feed Bin

JawCrusher

Stockpile Feed Conveyor

Crushed Ore Stockpile(11 hr Storage)

Mill Feed Conveyor

SAG Mill (625tph)Ball Mill(11.5MW)

Cyclones

Linear TrashScreen

Sump & PumpsPre-LeachThickener

Process Water Tank

Lime &Cyanide

Tailings Disposal atLa Quinua Leach Pad

Flocculant

NaHS &H2SO4

Flocculant

Flocculant

Lime

Carbon Treatment At La Quinua

H2SO4

NaOH

Recovered NaCNTo Mill Circuit

Flocculant

CONCENTRATE SALES

Feeder & Vibrating Grizzly

EXISTING ATAGGLOMERATOR

Leach Circuit(6 Tanks @ 24 hrs)

Dilution Water

SART Precip Thickener

SART NeutralizationTanks (4 Stages)

Gypsum Thickener

Gypsum Recycle

CarbonReturn

Stripping Columns(5 Installed)

Adsorption Columns(5 Installed)

Stripped Solution Tank

BarrenSolution

La Quinua CarbonAdsorption Circuit

Barren SolutionTo Leach Pad

CCD Wash Solution(LQ Barren)

Barren SolutionTo CCD Wash

CARBON COLUMNSAVR CIRCUIT

SART CIRCUIT

GOLD LEACH

PRIMARY CRUSHER(Existing)

Lime &Cyanide

CCD CIRCUIT5 Stages

Precip Filter and Bagging Plant Gypsum Recycle

To Mill

SAG & BALLMILLING

CRUSHED ORE STOCKPILE

Flocculant

PRE-LEACHTHICKENER

July 13, 2005

CRUSHING

Use existing agglomeration Crusher1500 TPH~9.5 h/d operationFeed Stockpile~11 hours live capacity in stockpileConsumables– Power and Steel liners

July 13, 2005

MILLING

New SAG and Ball MillD-26 Krebbs Hydrocyclones– Classify ground ore (80% -75 µm)Consumables– Power, steel balls, mill liners

July 13, 2005

PRE-LEACH THICKENING

Objective– Recover process water for grinding circuit– Thicken pulp for subsequent leaching to

optimize leach residence timeConsumables– Flocculent, anti-scalent, and power

July 13, 2005

GOLD LEACH

Slurry is mixed in large agitated tankswith the objectives:– Leach gold and silver from ore – copper is

leached as a by-product

Consumables– Power, cyanide, lime, low pressure air

July 13, 2005

CCD THICKENING AND WASHING

Purpose– Solids/liquid separation to produce metal/cyanide rich

solution for recovery of gold, silver, copper andcyanide

– Solids routed to mill sands 5 Stages of Thickeners- 28 – 30 metersdiameter Approx 600 m3/h of wash solution – 1.2:1 wasratio for >99% solute recovery Final thickener is also a high density mill sandsthickener – deeper cone

July 13, 2005

SART SOLUTION TREATMENT

Sulfidization, Acidification, Recycle, andThickening.– 1st CCD thickener overflow is treated in a

SART process to remove Cu and Ag– Precipitation of (WAD) metal cyanide

complexes – Ag, Cu, Zn– Cu and Ag sulfides sold as a concentrate– Neutralization with lime for gypsum removal– Au recovery via 7 stage CIC

July 13, 2005

SART SOLUTION TREATMENT

Batu Hijau – Copper SulfidePrecipitation Filter Press

Copper Sulfide product

July 13, 2005

CARBON ELUTION / REGENERATION

Will be performed in existing plants at La QuinuaFinal Au recovery in existing Merrill Croweplant/refinery at Yanacocha NorteObjective– Acid wash carbonate and organic material from

carbon– Concentrate gold from carbon to an enriched solution– Regenerate carbon activity– Return sized barren carbon to leach circuit

Consumables– Carbon, power, caustic, cyanide, anti-scalent, diesel

fuel, hydrochloric acid

July 13, 2005

AVR CYANIDE RECOVERY

Acidification, Volatilization, and Recovery

– Excess cyanide used in the mill will berecovered and reused in the mill to maintaincyanide balance

– Only in years where transition ores containinghigh copper values are treated

• Solution contacted with air in packed bed towers• HCN is stripped from the solution to the gas phase• Recycled cyanide is returned to the mill.

July 13, 2005

NEW REAGENT FACILITIES

CyanideLimeCaustic SodaCarbonFlocculantDiesel FuelAnti-ScalentSulfuric Acid

July 13, 2005

MILL SANDS DISPOSAL

High compression thickened mill sands.Dispose mill sands on the south section of theLQ pad.Mill sands disposal area has same foundationpreparation and liner system as La Quinuaheap leach.Heap leach and mill sands drainage systemsare continuous.Continuos monitoring program.

July 13, 2005

MILL SANDS CROSS SECTIONLA QUINUA PAD

July 13, 2005

PROJECT MILESTONE DATES

Submit AFE March 2005

Start EIS Workshops March 2005

Submit EIS January 2006

Start Detail Engineering Plant. November 2005

Start Bulk Earthworks Const. August 2006

EIS Approval January 2007

Start Mechanical/Elect. Const. March 2007

Mechanically complete November 2007

Start–up Plant January 2008

July 13, 2005

IMPORTANT RISKS

Manageable Risks– Expenditure schedule controlled by social

acceptance/permit progress.

Other Risks Considered– Political (Elections).– Social acceptance.– Metal prices.– Reagents & Consumable prices.– Escalation.