Chalcopyrite Molybdenite Pyrite Quartz
Virtual Museum ID: 19-AME991
Chalcopyrite is the most common ore mineral for copper and is a sulphide of iron and copper. Chalco comes from the Greek word chalko, meaning copper. Chalcopyrite is commonly found in sulphide deposits in most ore-forming environments. A characteristic deep brass yellow colour and iridescent green-to-purple weathering surfaces distinguish chalcopyrite from gold and sulphides such as pyrite.
Soft silvery-grey molybdenite is the main ore mineral for molybdenum. Molybdenum, often just called ‘moly’, is used to make alloys with other metals like iron. Adding molybdenum to steel makes it stronger, harder and more resistant to corrosion. It also has a very high melting temperature, so is very useful when added to alloys to make aircraft parts and industrial motors, which need to withstand high temperatures.
Pyrite is a common iron sulphide mineral found in many different geological settings. It has a brassy-yellow metallic colour that has caused many people to mistake it for gold, giving it the name “Fool’s gold”. Pyrite and gold can be quite easily distinguished from one another: pyrite is less yellow and much lighter and harder than gold, which can be scratched with a pocket knife. Pyrite often forms perfect cubes, which can grow to quite large sizes, because of its crystal structure. The word pyrite comes from the Greek word ‘pyr’ meaning fire, because it will spark if hit with other metal or stone objects.
Quartz is the second most abundant mineral on Earth, occurring in many different types of rocks. Although usually clear or milky white in colour, quartz can be found in a variety of colours because of impurities in the crystal structure. Pure quartz is made up of silicon and oxygen only, but atoms of other elements, like iron or titanium, often make their way into the quartz crystal structure. Some varieties of quartz, like purple amethyst, are considered to be semi-precious gemstones and have been used since ancient times to make jewellery and decorative objects.
This sample is from the Gibraltar mine in the Cariboo region of central BC, around 60 km north of Williams Lake. The mine is the second largest open pit mine in Canada.
The Gibraltar mine contains five main ore bodies: Gibraltar East, Gibraltar West, Gibraltar North, Granite Lake and Pollyanna. Production started in 1972 and continued until 1998, when metal prices dropped and the owner at the time, Boliden Resources, put the mine into care and maintenance. In 1999, Taseko Mines Ltd bought the mine and re-opened it in 2004. Production continues today.
The Gibraltar ore bodies are copper-molybdenum porphyry deposits, which are large, low-grade, high-tonnage deposits associated with granitic intrusions. Mineralization consists of veins of chalcopyrite with or without quartz, and molybdenite with quartz. The veins are mainly concentrated in areas that have been faulted and deformed.
The mine currently produces an average of 138 million pounds of copper at grades of 0.26% copper and 0.008% molybdenum.
The information listed below relates to the current holding location or collection that the sample is from, and whether the item is viewable at that location or is part of a private collection. Coordinates are given as guides, and we remind you that collecting specimens from these locations is not allowed. Caution is advised visiting such sites and Below BC assumes no responsibility for any injuries or trespassing charges that may occur as a result of the viewer entering these sites.
Original Collection:Association for Mineral Exploration (AME)
Virtual Museum ID:19-AME991
Date Added to VM:2018-02-15
Sample Origin:McLeese Lake, BC
Specific Site:Gibraltar Mine
Datum:10 (NAD 83)
Primary Features:Chalcopyrite Molybdenite Pyrite Quartz
Primary Mineral Formula:CuFeS2 · MoS2, FeS2
Primary Category:sulphide oxide
Advanced Geological Information
The following section provides geological data relating to the specimen or the site it was collected from, when available. Information has been obtained from various sources including private and government datasets but may not be up to date. Any geological time periods or ages listed often relate to the primary geology of the area, and may not be the actual date of an event such as mineral formation.
Geological Formation:Cache Creek Group
Geological Period:Mississippian to Triassic
Stratigraphic Age:251.9 to 323.2 Millions Years Ago
Geological Terrane:Plutonic Rocks, Cache Creek
Minfile ID:093B 051
The Gibraltar East deposit is located near the eastern margin of the Stikine Terrane west of Granite Mountain in south-central British Columbia. The Stikine Terrane is dominantly oceanic and became amalgamated with the Quesnel Terrane to the east probably during Triassic times. The dominant rock types in the region are metabasalt, limestone and argillaceous metasediments of the Mississippian to Triassic Cache Creek Group. These are intruded by the dioritic to quartz dioritic Late Triassic Granite Mountain pluton and the (?)Cretaceous Sheridan Creek pluton. The Granite Mountain pluton has been dated at 204 ±6 Ma by potassium-argon dating of hornblende (CIM Special Volume 15, page 195). Jurassic sedimentary rocks overlap both the Cache Creek and Quesnel terranes to the north and east of the plutons. Older rocks are largely obscured by Plateau Basalt of probable Miocene age, to the west.
The Granite Mountain pluton has been affected by regional metamorphism (greenschist facies) and deformation along with the enclosing Cache Creek Group. The Cache Creek Group and the margins of the Granite Mountain pluton record effects of ductile deformation. The main body of the pluton has been cataclastically deformed.
The Gibraltar orebodies lie along the southern and western flanks of Granite Mountain at elevations between 914 and 1231 metres. The Gibraltar East deposit is one of the five orebodies that comprise the Gibraltar mine, the others are: Pollyanna (093B 006), Gibraltar West (093B 007), Gibraltar North (093B 011) and Granite Lake (093B 013), with several small similar occurrences in the area (Sawmill (093B 051)).
The orebodies are hosted by the Granite Mountain pluton with ore mineralization almost entirely confined to the Mine Phase Tonalite portion of the Granite Mountain pluton. The Mine Phase Tonalite appears to form a thin outer shell about the main body of the pluton and contains approximately 30 per cent quartz, 50 per cent saussuritized plagioclase feldspar and 20 per cent chlorite. Varying degrees and types of alteration are present and readily visible in the Mine Phase Tonalite. Economic sulphide mineralization in the Mine Phase Tonalite is usually associated with sericitization and chloritization. The tonalite has been strongly deformed by shearing and mineralization is strongly associated with this deformation. Mineralization is generally accompanied by alteration and is confined to deformational structures. These structures comprise small and large shear zones, foliation planes, short veins and various dilatant structures.
As a whole, the Gibraltar mineralized system is comprised of numerous structural hosts for economic mineralization ranging from highly mineralized shear zones to complex sets of sheeted shear veins commonly referred to as oriented stockworks. The oriented stockwork is the prevalent structural host within the Pollyanna Mineralized System.
In Geological Fieldwork 1998 (Ministry of Energy and Mines), pages A1–A15, the origin of the Gibraltar ores are found to be associated with intensely foliated to schistose rocks, which have been labeled mineralized shear zones. The Granite Mountain Batholith is now thought to have been tectonically emplaced into the Cache Creek, rather than having been intruded into it.
Mineralization consists of pyrite, chalcopyrite, molybdenite, magnetite, bornite and cuprite. Associated alteration minerals are quartz, sericite, chlorite, epidote and carbonate. The Gibraltar deposits all show secondary oxidation and secondary enrichment with the formation of chalcocite as coatings and as replacement of pyrite and chalcopyrite.
The Gibraltar mine area has a long history of mineral exploration, beginning around 1917, when Joseph Briand and partners explored copper-bearing quartz veins on the Rainbow group of mineral claims. These original showings are believed to lie about 60 metres west of the current Pollyanna pit. Prospecting in the Granite Mountain area continued on through the 1920s and by 1928, the Sunset shear zone was discovered west of the Rainbow Group on ground held by G.F., H.B., and J.F. Hill. The discovery area is now known to have been the exposed southeast end of the Gibraltar West orebody. The Rainbow showings and the Sunset shear zone provided the focus for further prospecting up to at least the 1960s. In 1949, both showings were held by C.E. Johnson and R.R. Moffat, who made a half-ton shipment of ore from the Rainbow Group to the Tacoma smelter. By 1956, E. Kinder, T. Matier, and R.L. Clothier had acquired the properties, and in 1957, had completed a 36 metre adit into the Sunset zone. Both properties were later allowed to lapse. In 1962, John Hilton restaked the general area of the Sunset zone, which was later to become the Gibraltar property, and in 1963, Robert Glen relocated the Pollyanna property, including the former Rainbow showings.
The first major company on the scene was Keevil Mines Ltd. who optioned the Pollyanna and Gibraltar properties in 1962, and proceeded to carry out extensive geophysical and geochemical surveys before terminating the options in 1964. Gibraltar Mines then took over the property and started a drilling program, totalling 3,300 metres. They completed 52 drillholes before the property was optioned to Cominco and Mitsubishi Mining in 1966. One drill hole (C-23) returned values of 0.50 per cent copper over 39.8 metres and sampling of an adit being driven on the south bank of Copper creek returned an average of 1.28 per cent copper from 15 samples (Property File Cyprus Anvil Caldwell, E.H., 1966). In 1967, Cominco Limited performed 14 diamond-drill holes totalling 1,409 metres. Canex Placer Limited and Duval Corporation jointly explored the Pollyanna property in the late 1960s and in 1969 optioned the adjacent Gibraltar property. Canex Placer purchased Duval's interest in 1970, to hold both properties.
Production began at the Gibraltar mine on March 8, 1972 and the official opening was on June 17 of that year. The operating company, Gibraltar Mines Limited, was owned 68.1 per cent by Placer Dome Inc. (formerly Canex Placer Ltd.). In total, four major orebodies have been brought into production on the Gibraltar property; the Pollyanna (093B 006), Gibraltar East (Gib-East) (093B 012), Gibraltar West (Gib-West) (093B 007) and the Granite Lake zone (093B 013).
Reserves at start-up were 326.6 million tonnes grading 0.371 per cent copper and 0.016 per cent molybdenum. These reserves included: Gibraltar East, 136.0 million tonnes; Granite Lake, 108.9 million tonnes; Pollyanna, 73.5 million tonnes; and Gibraltar West, 8.2 million tonnes.
The Sawmill zone (093B 051) was outlined in 1979 about 6 kilometres south of the plant site. In 1980, a 27.2-million tonne extension to the Pollyanna zone was discovered beyond the eastwall of the Stage I pit. The Gibraltar North (093B 011) orebody was discovered in 1990. The mining reserves as of December 31, 1992 were:
These are a combination of proven and probable reserves at cutoff grades of 0.18 per cent copper for Gibraltar East and 0.20 per cent copper for the other ore zones, and at a strip ratio of 1.20:1.
That part of the mineralized inventory deemed uneconomic under current conditions has been classified as a mineral resource. As of December 31, 1992, the Gibraltar mineral resources were:
A 0.20 per cent copper cutoff was used for Pollyanna and Granite Lake, and a 0.18 per cent copper cutoff was used for the other zones. Milling commenced in March 1972. From that date to December 31, 1992, a total of 241,000,000 tonnes of ore averaging 0.360 per cent copper had been milled. Major ore production was from the Pollyanna, Granite Lake and Gibraltar East zones. A small tonnage was mined from Gibraltar West. Neither Gibraltar North nor the Sawmill have been mined.
The average daily mine production was about 37,700 tonnes of ore and 57,500 tonnes of waste rock (Property File - Briefing notes from a mine tour on February 12, 1993, Rick Meyers (Kamloops District Geologist)).
In 1994, recoverable reserves were 54 million tonnes grading 0.38 per cent copper and 0.54 gram per tonne gold (News Release, March 21, 1994, Gibraltar Mines Limited).
Mining and milling resumed in September 1994 after a suspension of operations on December 1, 1993 due to low copper prices. Reserves estimated at January 1, 1995 were 166,259,440 tonnes grading 0.291 per cent copper and 0.009 per cent molybdenum (Information Circular 1996-1, pages 6, 7).
Proven and probable reserves of all ore deposits as of January 1, 1996 are 179.0 million tonnes, grading 0.297 per cent copper and 0.009 per cent molybdenum (Gibraltar Mines Limited, Annual Report 1995).
Combined (proven and probable) reserves for Gibraltar East are 49.2 million tonnes, grading 0.281 per cent copper and 0.008 per cent molybdenum (Gibraltar Mines Limited, Annual Report 1995).
In 1996 production was from the Gib East pit, but reserves there were exhausted by early 1998. Subsequent production will be from the Pollyanna stage 4 pit (093B 006) and Granite Lake stage 3 and 4 pit developments (093B 013). The company reported a 12-year mine life, but the estimate excludes reserves at the Gib North and Sawmill zones (R. Lane, personal communication, 1996).
Production from 1972 to 1998 totals 325,696,830 tonnes yielding 100,174,052 grams of silver, 143,368 grams of gold, 876,712,378 kilograms of copper, and 9,036,601 kilograms of molybdenum.
Westmin Resources Ltd. acquired the mine on October 15, 1996. Proven and probable sulphide reserves (December 31, 1996) for the Gibraltar East, Granite Lake and Pollyanna deposits total 142,544,000 tonnes grading 0.303 per cent copper and 0.009 per cent molybdenum. In addition, oxide reserves for the Connector zone and Pollyanna Stage IV pit total 3,039,000 tonnes grading 0.273 per cent copper (T. Schroeter, personal communication, 1997). The Gib North and Sawmill zones are not part of the mineable reserves.
Westmin Resources Ltd. is owned by Boliden Limited. Operations ceased by the end of 1998.
Total mineable sulphide ore reserve for the Gibraltar as of December 31, 1997, is 184.4 million tonnes grading 0.310 per cent copper and 0.010 per cent molybdenum. The total leachable ore reserve is 16.3 million tonnes at an acid-soluble grade of 0.151 per cent copper (Exploration in BC 1997, page 22).
In mid-Janaury 1999, Boliden began to shut down the mine, with full closure by February 1999. In April 1999, Taseko Mines Limited announced that they will acquire the Gibraltar mine.
Gibraltar Mine Reserves as of December 31, 1998 were:
Taseko Mines Limited acquired the Gibraltar Mine in 1999.
Hunter Dinkinson Inc. is the management company that provides the management, financial and corporate development services to Taseko Mines, and Gibraltar Mines Ltd. is a wholly owned subsidiary of Taseko.
Gibraltar Mines Ltd., in a joint venture with Ledcor Mining Ltd, resumed operations in the Pollyanna pit (093B 006) in October, 2004. Sulphide resources, using a 0.2% copper cutoff grade, stand at 745 million tonnes. Included in this estimate are measured and indicated resources of 149 million tonnes grading 0.31 per cent copper and 0.01 per cent molybdenum in the 12-year mine plan, plus additional measured and indicated resources of 596 million tonnes grading 0.28 per cent copper and 0.01 per cent molybdenum (N Miner, Nov. 24, 2003).
In 2003, Taseko Mines Ltd. completed the largest diamond drilling program in the region on its Gibraltar (MINFILE 093B 005, 008, 011–013, 051, 061–063) property. The property surrounds the inactive Gibraltar mine, which has been on standby status since 1998. A total of 22,746 metres of drilling took place in 194 diamond-drill holes. The primary target was the 98 Oxide Zone, centred about 1.1 kilometres east-northeast of the Pollyanna pit. The 98 Oxide zone occurs in propylitically altered and strongly foliated quartz-rich granodiorite or trondhjemite. Oxide minerals are dominated by malachite, azurite, cuprite and tenorite, and chalcopyrite occurs with pyrite and molybdenum in late, cross-cutting quartz veins. Other drill targets included the TK Zinc and Highway zones.
Gibraltar Mines Ltd., in a joint venture with Ledcor Mining Ltd, resumed operations in the Pollyanna pit (093B 006) in October, 2004. Sulphide resources, using a 0.2% copper cutoff grade, stand at 745 million tonnes. Included in this estimate are measured and indicated resources of 149 million tonnes grading 0.31 per cent copper and 0.01 per cent molybdenum in the 12-year mine plan, plus additional measured and indicated resources of 596 million tonnes grading 0.28 per cent copper and 0.01 per cent molybdenum (N Miner Nov. 24, 2003).
Fine tuning of the copper and molybdenum circuits took place throughout the first and second quarters of 2005 resulting in significant improvements in recoveries for both metals. Diamond drilling and condemnation drilling totaled 6990 metres in 40 holes. At the end of 2005, Gibraltar mineral reserves in the proven and probable category (at 0.20 per cent cut-off) were 176 million tonnes grading 0.31 per cent copper and 0.01 per cent molybdenum; Gibraltar mineral resources (measured and indicated) (at 0.20 per cent cut-off) were 557 million tonnes grading 0.28 per cent copper and 0.008 per cent molybdenum (Taseko Mines Press Release, December 12, 2005).
The 2006 drilling program totalling 18,750 metres in 67 drillholes increased reserves further for 2007. Reported Proven reserves were 279 million tonnes grading 0.313 per cent Cu and 0.009 per cent Mo and reported Probable reserves were 70 million tonnes grading 0.296 per cent Cu and 0.010 per cent Mo. These were calculated using a 0.20 per cent Cu cut-off (Taseka Mines Ltd., 2007 Annual Report). In early 2008 a two phase expansion was completed putting the estimated mine life at 17 years.
In December 2008 Taseko released increased Reserve and Resource amounts due to further drilling which confirmed an extension of the Gibraltar mineral deposit. Reported combined Proven and Probable reserves were 428.6 million tonnes grading 0.315 per cent Cu and 0.008 per cent Mo. Reported Measured Resources were 542.2 million tonnes grading 0.302 per cent Cu and 0.008 per cent Mo and Indicated Resources were 327.5 million tonnes grading 0.290 per cent Cu and 0.008 per cent Mo. All were calculated using a 0.20 per cent copper cut-off (News Release December 11,2008 www.stockwatch.com).
Taseko's website show updated Reserve and Resource amounts as of December 31, 2009. Reported combined Proven and Probable reserves were 459 million tonnes grading 0.315 per cent Cu and 0.008 per cent Mo. Reported combined Measured and Indicated resources were 959 million tonnes grading 0.298 per cent Cu and 0.008 per cent Mo. All were calculated using a 0.20 per cent copper cut-off (http://www.tasekomines.com/tko/Gibraltar.asp).
Taseko Mines released updated reserve and resource amounts as of March 31, 2011. Calculated at 0.20 per cent Cu cut-off. (Stockwatch News Release May 10, 2011):
Taseko Mines released a report in 2015 with updated reserves and resources (Technical Report on the Mineral Reserve Update at the Gibraltar Mine, June 15, 2015):
Category Amount Cu(%) Mo(%)
Measured 753,000,000 0.26 0.008
Indicated 238,000,000 0.24 0.008
Indicated 991,000,000 0.25 0.008
Inferred 46,000,000 0.22 0.004
Probable 679,000,000 0.26 0.008