Gibraltar mine is the second largest open pit copper mine in Canada, which is located near Williams Lake in British Columbia. The Gibraltar deposit is a copper-molybdenum porphyry. The principal primary mineral is sulphide mineral Pyrite and Chalcopyrite. As the reserves announcement at December 31, 2008, Gibraltar mine got a mine life to at least 2035. After completing the Phase I & II projects, the Gibraltar mine achieves the capacity of 55,000 tonnes per day. There are two kinds of mineralization ores, which are sulfide ore and oxide ore. The former one could be done by the regular mineral processing method, and the latter one should be done by the method called SX/EW (solvent extraction electro-winning). Gibraltar mine also updated their mining and processing equipments for the development. Additional, Gibraltar mine has done a great job on the environment and sustainability issues.
The Gibraltar copper-molybdenum mine is located about 65 km northwest of Williams Lake in south-central British Columbia with a well-developed infrastructure. The mine is accessible by a combination of highways (97) and paved roads, and it is close to a rail network that provides service for shipment of copper concentrates through the Pacific Ocean port of North Vancouver (Taseko, 2009).
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Figure 1: Gibraltar - Regional Location
(Source: Taseko, 2009)
The Gibraltar mine is the second largest open pit copper mine in Canada (Gibraltar, 2009). The mine is a 46,000 tonnes per day operation with a life of mine average annual production of 100 million pounds of copper and 1.1 million pounds of molybdenum. The mine is undergoing an expansion and modernization project that will increase annual copper production capacity to 115 million pounds by 2011 (Taseko, 2009).
Figure 2: The Satellite View of the Gibraltar Mine
(Source: Google Earth, 2009)
The development of the mine is as follow (MREP, 2009),
1910 The Gibraltar ore deposit was first discovered
1971 Originally built by Placer Development
1972 Began operation, 24 hours/day, 7 days a week
1998 Shutdown by Boliden due to the low copper prices after 26 years operation
1999 Acquired by Taseko Mines Limited (100%), put on standby
2003 Copper prices begin to increase, exploratory drilling program began
2004 Reopened, and the SX-EW plant was being restarted
2006 An extensive drilling program discovered additional 30% of reserves
2008 Gibraltar proven and probable reserves are increased by 28% to 472 million tonnes, or 2.7 billion pounds of recoverable copper extending mine life to 2035 (Gibraltar, 2009)
2009 Prosperity Environmental Assessment report is submitted to both Provincial and Federal governments
Figure 3: Gibraltar - Minesite layout
(Source: InfoMine, 2009)
The Gibraltar deposit is a copper-molybdenum porphyry. The principal primary mineral is sulphide mineral Pyrite and Chalcopyrite. The ore occurs in seven separated zones, all within a 204 million year old granitic rock. The mineralized zones are Gibraltar East, Pollyanna, Gibraltar West, Gibraltar West Extension, Gibraltar North, Connector and Granite Lake (MREP, 2009).
"The pits occur within the Granite Mountain batholith in a broad zone of shearing and alteration. The Sawmill zone lies about 6 kilometers to the south, along the southern edge of the batholith, within a complex contact zone between the batholith and Cache Creek Group rocks" (InfoMine, 2009).
The mine site covers approximately 109 square kilometers and consists primarily of 251 mineral claims and 30 mining leases (InfoMine, 2009). When the mine restarted in 2004, reserves were only 149 million tonnes, or approximately 12 years of mine life. The mission for the Gibraltar mine management team is to increase reserves and extend the mine life. Over the past four years, over $20 million has been spent on three major drill programs, each program resulting in a significant increase to proven and probable reserves. The most recent drill program, in the spring and summer of 2008, resulted in a 28% increase to proven and probable reserves, as announced in December 2008. Under present reserves, the mine is expected to remain in current operation situation until at least 2035. Here is the announcement at December 31, 2008.
Table 1: Gibraltar Reserves and Resources at December 31, 2008
Category (at 0.20% Cu Cut-off)
Cu (B lbs)
Cu (B lbs)
Proven & Probable Reserves
Measured & Indicated Resources
Always on Time
Marked to Standard
(Source: Gibraltar, 2009)
Taseko Mines Limited Owns the 100% of the Gibraltar mine's interest. The production of the Gibraltar mine is showed as below:
Table 2: Summary of the Operating Statistics
Total tonnes mined (millions)
Tonnes of ore milled (millions)
Copper grade (%)
Molybdenum grade (%)
Copper recovery (%)
Molybdenum recovery (%)
Copper production (millions lb)
Molybdenum production (thousands lb)
Copper production costs, net of by product credits, per lb of copper
Off property costs for transport, treatment (smelting & refining) & sales per lb of copper
Total cash costs of production per lb of copper
Notes to table:
1 Q2 2009 relates to the 6 months ending June 30, 2009
2 Fiscal 2008 relates to the 15 months ending December 31, 2008. (Source: Taseko, 2009)
From the above table, we can find that the stripping ration of the Gibraltar mine is at a significantly reduced compared with the prior years. According the Taseko mines Second Quarter Results, the Gibraltar mine "operated for the first six months of 2009 under a plan initiated in November 2008, based on 45,000 tonnes per day mill" (Taseko, 2009).
"This new operational plan along with declining input costs, and the realization of the Phase I expansion, resulted in substantially reduced costs compared to prior years. The mine is currently reviewing a return to deposit average strip ratio based on recent strength in copper and molybdenum demand and corresponding increases in metal prices" (Taseko, 2009).
As known, the market of metals suffered a historical hardest time during 2008 and 2009, due to the global financial crisis. However, the total cash cost of production per lb of copper of Gibraltar mine declined sharply to US$1.23 in 2009. Therefore, even though the price of copper has declined, Gibraltar's profit margin has still improved.
Mining at Gibraltar is carried out using conventional open pit methods in the Pollyanna on the east side of the property, which is 1.8 km long by 0.7 km at its widest point. Drilling is done by a fleet of 3 rotary blast hole drills, which drill 32 cm diameter holes and 15 m deep. Blasting is done two to three times a week and creates 13.7 m high benches in the pit wall (MREP, 2009).
"Blasted ore is loaded by one of three P&H shovels into one of eleven haul trucks that hold between 205 and 240 tonnes each. They haul the ore about 2.4 km to a gyratory crusher located above the pit near the mill building. The haul trucks transport most waste rock to dumps along the north wall of the Pollyanna pit where they are gradually filling in the pit. Some waste rock that contains oxidized copper mineral ore is hauled out of the pit to a stockpile for refining process" (MREP, 2009). According to the Annual General Meeting Presentation, the construction for the Phase I expansion and modernization was completed in January 2008, achieving 46,000 tonnes per day steady state. And Phase II expansion project was completed in March 2009, to increase the capacity to 55,000 tonnes per day (Gibraltar, 2009).
Gibraltar mine acquired new mining equipment in place to handle higher mill rates, as below.
Figure 4: New Mining truck - 240 ton TEREX MT 4400AC
(Source: TEREX, 2009)
Figure 5: New Mining Shovel - P&H 4100C Electric MS
(Source: Zlotnikov, 2009; P&H Mining Equipment, 2009)
Figure 6: Mill Flowsheet of Gibraltar Mine
(Source: Gibraltar, 2008)
Comminution is a process, which breaks the rock from large chunks into smaller pieces and then to finer particles. There are crushers used for breaking the large rocks and grinder to finer particles.
In Gibraltar mine, the new feed & grinding circuit described as, ROM goes in to a gyratory crusher (54x74) followed by four parallel secondary crushers (13x84) in closed circuit. Then, the crushed ores are conveyed into the 34 feet SAG mill through a 45Â° conveyer at a rate of 49,000 tonnes per day. The ore was distributed to 6 ball mill circuits, which pulverize the ore to sand. Then, the material discharged from mills is separated by hydro-cyclones (The overflow<0.5mm, underflow>0.5mm). In addition, there are 2 re-grinding mill, which are used to reduce the rougher flotation products from under 0.5 mm to under 0.1 mm (Chen, 2008).
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The froth flotation is actually a physical process that uses surfactants and wetting reagents to increase the hydrophobicity of the minerals. The sulfide minerals, such as chalcopyrite and bornite, are water-repellent (hydrophobic). Therefore, froths are added to the slurry to make collector (bubbles) stronger enough to hold the attached minerals to the surface (EduMine, 2009).
From the mills the slurry is piped into flotation cells, which float a mixed copper and moly concentrate, which is piped to a molybdenum flotation circuit where the moly and copper concentrates are separated. These concentrates pass through a thickener before being dried. In the Copper-Moly Separation Circuit, NaHS is added in this circuit as a copper depressant in order to prevent the copper from floating. Meanwhile, the moly can still float (Chen, 2008).
Figure 7: Original and Modernized Flotation Circuit
(Source: Gibraltar, 2009)
In the early stage, Gibraltar also operated a SX/EW (solvent extraction electro-winning) plant on site to recover cathode copper from copper oxide minerals, namely azurite, malachite, chalcocite and cuprite. The process involved dissolving these minerals in sulphuric acid with the help of naturally occurring bacteria in outdoor piles of waste rock, followed by electroplating the dissolved copper metal from the acid in the enclosed refinery building. Gibraltar's SX/EW plant produced around 38,430 tonnes of cathode copper from 1986 to 1999. The facility was reopened in 2007 and is once again producing copper cathode at a rate of 1.1 million kilograms per year (MREP, 2009).
The mainly purpose of the SX/EW plant is to extract copper from the pregnant leach solutions (PLS) collected from the site's leach dumps and heap leach pad. "The process takes PLS and extracts the copper in three extraction mixer-settlers. The copper is extracted through a liquid ion-exchange reagent carried in kerosene." The copper is selectively transferred to the organic phase, due to the chemical reaction. The loaded organic phase is separated and flows to a strip mixer-settler where the copper is transferred from the organic to the electrolyte. "The electrolyte is filtered and heated before being passed through the electro-winning cells where the copper is plated out on stainless steel cathodes. Periodically, the cathodes are removed from the cells, washed and the copper sheets mechanically harvested. The resultant high quality cathode copper is bundled and sold" (InfoMine, 2009).
ENVIRONMENT AND SUSTAINABILITY
Gibraltar Mine also locates in the heart of BC's Cariboo Chilcotin plateau, which is a high interior region of mixed coniferous forests and grasslands. "It is home to many different types of wild animals, deer, moose, caribou, black bears, wolves, as well as livestock." The purpose of Gibraltar's reclamation plan is to return the site to the wild animals. In 1999, an environmental assessment complete when Taskeo bought the mine concluded the cost to be $32.7 million for both reclamation and water management. Final details have not been mapped out, but so far grass and legume vegetative covers have been established on disturbed land to immediately control wind erosion and provide forage (MREP, 2009).
Meanwhile, Gibraltar formed a successful partnership with the Cariboo Regional District (CRD), which designed, built (2003) and now maintains a landfill on one of the mine's waste rock dump. The landfill accepts 13,000 tonnes of household waste from CRD communities each year (MREP, 2009). The public gave a agree vote to the landfill site program, because they believed that establishing such a facility at a mine site would be environmentally, socially and economically sustainable, and could be developed as a public private partnership (InfoMine, 2009).
"Under the agreement, Gibraltar would remain responsible for the waste rock and drainage below the landfill and the Cariboo Regional District would be responsible for the air space above the waste rock" (InfoMine, 2009).
The benefits of establishing the landfill at the Gibraltar mine's waste rock dump are numerous: (InfoMine, 2009)
Located on industrial land, with no need to build roads and disturb new ground, environmental impact and additional cost of construction were eliminated.
Large on-site mine equipment could build the landfill at half the cost.
The landfill would compliment mine reclamation.
The mine's extensive surface and groundwater monitoring system would also serve the landfill.
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