Overview
The Kalgoorlie operation consists primarily of the Super Pit open-pit mine, located along the Golden Mile ore bodies which were previously mined from underground. The large open-pit mine is located adjacent to the town of Kalgoorlie approximately 550 kilometres east of Perth, Western Australia. Barrick holds a 50% interest with Newmont Mining Corporation holding the remaining 50% interest.
Kalgoorlie is an open-pit, truck-and-loader operation. Ore is treated at the Fimiston mill, with the resulting sulphide concentrates then roasted and leached at the Gidji roaster, located approximately 20 kilometres north of the main Kalgoorlie operations. Gold-laden carbon from the Gidji roaster is also processed at the Fimiston mill. Concentrates that cannot be processed by the roaster is treated by two ultra-fine grinding mills.
In 2009, production of the mine was 690koz. Proven and probable mineral reserves as of December 31, 2009 is estimated at 8.4 million ounces of gold.
Location
The Kalgoorlie properties consist of 58 mining leases and 104 prospecting licenses covering 23,000 hectares, located adjacent to the town of Kalgoorlie, 550 km northeast of Perth, Western Australia.
Geology
GOLD in greenstone belt-hosted structural zone deposits. The goldfield consists of a number of discrete deposits, of which the most significant are the Golden Mile, Mt Charlotte (3 km north of the Super Pit), Mt Percy and Hannan's North. The Golden Mile Deposit accounts for about 90% of gold production from the field.
The gold deposits are largely hosted by ultramafic and mafic volcanic rocks and mafic sills, with the Golden Mile Dolerite, a mafic sill, the most important host to mineralisation. The stratigraphy has been intensely deformed by folding and faulting.
The Golden Mile, an intensely mineralised, steeply dipping shear system, is divided into two parts. The Eastern Lode System comprises a 'swarm' of lodes (areas of pyritic and hydrothermal alteration) with mineralisation confined to shoots at lode-lode/lode-fault intersections. The Western Lode System is less complex, with fewer lodes than the Eastern System, but the lodes are persistent and well defined.
Gold occurs as native gold and as gold and gold-silver tellurides. Native gold often occurs within or marginal to pyrite grains. The ores are mineralogically complex and refractory. As of 2000, production was sourced from two mines, the Super Pit and Mt Charlotte.
Operation
The most important component of the Kalgoorlie operations is the Super Pit open pit mine (also referred to as the Fimiston open pit). The Super Pit is a consolidation of several older pits which mined 10 Mt ore in 1993. The Fimiston underground operated through 1 of 5 shafts (Dec/91) using blast hole stoping and was closed in Mid-1992. The Mt. Percy pit was mined out in Jul/92. The Charlotte underground uses bulk underground methods and conventional loader trucks to mine 1.6 Mt/y (Dec/93); primary crushing is done underground.
The operations include 5 mills (1 closed in 1992). The Fimiston is a 13,200 t/d mill with CIP leaching and refractory sulphide flotation circuits which process ore from the Super Pit and Mt Charlotte. The Croesus is a 2,700 tpd mill with CIP and refractory sulphate ore flotation circuits which process the ore from the Super Pit ore. The Mt. Percy is a 2,250 t/d mill with a CIP circuit which processes ore from Mt Percy and the Super Pit. The Paringa was a 600 tpd flotation mill processing refractory ore from the Fimiston underground and closed down in mid-1992. Flotation concentrates are treated in 2 roasters located 11.2 miles away in Gidji and then returned for CIP extraction.
The Kalgoorlie goldfield was discovered in 1893. Activity was initially concentrated at the northern end of the field, close to Mt Charlotte, where gold occurred in quartz veins and surficial deposits familiar to the early prospectors. Two years elapsed before the unusual ferruginous and oxidised Golden Mile lodes at the southern end of the field were recognised. Production reached a peak in 1903 when 1.2 million ounces were produced from ore grading an average 41 g/t. Production gradually declined as grade decreased with depth and primary, refractory ore was encountered. The revaluation of gold in 1932-33 led to a major revival but production again declined from 1960 onward and, by 1975, all operations on the Golden Mile had ceased. Only the highly mechanised Mt Charlotte mine remained in production. The Kalgoorlie operations consist of four mines (two open pit and two underground), five mills and two roasters. The two open pit mines are the Super Pit (Golden Mile) and the Mt Percy. The two underground mines are the Mt Charlotte and the Fimiston.
Following the sustained rise in the gold price from 1979, Golden Mile operations progressively reopened, applying modern mining and treatment methods. A progressive rationalisation and consolidation of ownership of the field followed, culminating in integration of operations under a single management company, KCGM, in 1989.To Dec/01, the Kalgoorlie goldfield has produced 48 million ounces of gold.
Processing
Kalgoorlie is Australia's largest gold plant, and ranks as the ninth largest gold producer in the world. The mill and plant process approximately 13.0 million tonnes per annum at a grade of 2.0 to 2.5 g/t Au. The plant recovers approximately 800,000oz per year of gold.
Ore is treated at the Fimiston mill, with the resulting sulphide concentrates then roasted and leached at the Gidji roaster, located approximately 20 kilometers north of the main Kalgoorlie operations. Gold-laden carbon from the Gidji roaster is sent to the Fimiston mill for processing. Processing is supplemented by two ultra-fine grinding mills that treat concentrate which cannot be processed by the roaster. Doré is shipped to Perth for refinement into gold bullion.
Fresh water is supplied under allocation from the state water system and piped from Perth. Other process water comes from salt water taken from wells and the underground mine. Power is provided under a power supply agreement with Newmont Power. The SAG mill alone uses 12 megawatts of power.
The mill has two grinding circuits: a 36 foot SAG mill and two ball mills ; and a 24 foot SAG mill and one ball-mill. Each of Fimiston's two Ball Milling Circuits has 2 300tph Knelson Concentrators, 1 5.5 m x 3.1 m vibrating screen, 1 10/8 Warman Gravity Feed Pump, and 1 3/2 Warman Concentrate Transfer Pump. The Mt. Charlotte gravity circuit has a 300tph KCXD48 Knelson Concentrator, a Schenck 4.3 m x 2.5 m vibrating screen, a 8/6 Warman Gravity Feed Pump, and a 3/2 Warman Concentrate Transfer Pump. In 2004 the mine commissioned a gravity circuit consisting of five Knelson KC-XD48 Concentrators and a ConSep ACACIA CS6000 concentrate leach reactor.
