Brunswick Lead and Zinc Mine, New Brunswick, Canada

The Brunswick lead/zinc mine, located 35km southwest of Bathhurst, New Brunswick, was formerly owned and operated by Noranda. In June 2005, Noranda merged with its 59%-held subsidiary, Falconbridge, with the ‘new Falconbridge’ being taken over in mid-2006 by the Swiss-based company, Xstrata. Brunswick now operates within Xstrata’s zinc division, producing lead and zinc concentrates with byproduct copper, silver, gold, bismuth, antimony and cadmium. Employing around 800 people, Brunswick treats about 3.6Mt/y of ore, and is the world’s largest underground zinc mine with a cumulative output to the end of 2005 of over 110Mt of ore. Its output is refined at the company’s Brunswick lead smelter and at the CEZinc refinery. GEOLOGY AND RESERVES The ore is contained in up to ten massive sulphide lenses within folded and uplifted lead-zinc, pyrite and copper zones. The metals occur as extremely fine-grained mixtures of chalcopyrite, galena, sphalerite and pyrite, together with gold, silver and other metals. At the end of 2005, proven and probable reserves totalled 14.7Mt grading 0.36% copper, 8.77% zinc, 3.53% lead and 104g/t silver, sufficient for a further four-to-five years’ production. MINING METHOD The 1,125m-deep mine is accessed by a vertical shaft and worked by two methods; the older cut-and-fill method allows the ore to be mined steadily from bottom to top and backfilled with waste rock, leaving a working platform. However, the more efficient open stoping is preferred. Pillars are removed later. Blasted ore is retrieved by remote-controlled load-haul-dump (LHD) machines for transport to ore passes leading to one of the three crushing plants. One recent innovation used is the ‘Weasel’, a unit that can be operated by remote control for drilling and charging blastholes in open stopes. Each crusher has two 1,500t-capacity, run-of-mine ore storage silos. A jaw crusher and two gyratory crushers reduce the ore to minus 150mm before conveyance to the No.3 shaft silos for hoisting to surface in skips. PROCESSING The concentrator design capacity is 10,500t/d of complex lead, zinc, copper and silver sulphide ore. During 2002 an average of 9,560t/d of ore was treated in the mill with a zinc recovery rate of 87.5%. The head grade was around 3.6% lead, 9.7% zinc, 0.36% copper and 105g/t silver. The ore is crushed to –25mm in a cone crusher and stored in fine ore bins (total capacity 9,000t). The subsequent grinding circuit consists of a rod mill from which the outflow passes to hydrocyclones. The rod mill oversize is recycled through a ball mill before re-entering the hydrocyclones. The undersize pulp, containing sphalerite, chalcopyrite, galena, sphalerite/galena combined and gangue minerals, feeds the sequential flotation circuits to produce individual zinc, copper, lead and bulk sulphide concentrates. Zinc is recovered first, with the rougher tailings feeding the copper recovery stage. Copper tailings proceed to lead upgrading and bulk concentrate recovery. Lead upgrading uses reverse flotation to float off pyrite, which is sent to the final tailings. The by-product is lead concentrate containing 40% lead. In the bulk circuit, combined lead and zinc is floated, producing a concentrate containing 39% zinc and 19% lead. The copper concentrate contains 23.5% copper and the zinc concentrate contains 52.5% zinc. Concentrates are dewatered to 30–40% moisture. Vacuum filters reduce the water content in the zinc, lead and bulk concentrates to around 17%, with further kiln drying to 7% moisture, while the copper concentrate is dried using pressure filters. Production during 2005 was 265,648t of zinc in concentrate, 5,894t of copper in concentrate and 75,417t of lead in concentrate, plus 5.9Moz of silver. TRANSPORT AND MARKETS Copper and zinc concentrates are shipped to worldwide markets as raw concentrates. Lead and bulk concentrates undergo further refining in the company smelter at Belledune. The smelter separates out copper matte, antimony-lead alloys, silver-gold doré and bismuth alloys in successive steps. EXPANSION PROJECTS Recent developments have included the commissioning of a paste backfill plant to simplify the backfilling process underground, and the installation of an SAG mill to give better grinding performance in the preparation of flotation feed. ENVIRONMENT The Brunswick commitment to the wellbeing of communities while sustaining the natural environment is demonstrated by the Daly Point wetland project, the Nepisiquit salmon enhancement project and the company’s environmental awareness programme. Acid mine drainage is now treated in the new high-density sludge treatment (HDST) plant at the No.12 site. A high-density lime (HDL) treatment process is used to reduce the acidity and water content. From : Mining-Technology.com		The surface installations at the Brunswick No.12 mine.
		Three-dimensional image of the No.12 orebody.
		Ore is recovered by blasting then dumping, followed by crushing and finally hoisting to the surface for treatment.
		Oversize rocks in the stopes are drilled and charged using the Weasel remote-controlled rig.
		Using a raiseborer to drill orepasses from one level to the next.
		Shotcrete is used to control the rock surfaces and to provide roof support.
		Water sampling is part of the mine’s continuing environmental protection programme.

Porgera Gold Mine, Papua New Guinea

The Porgera gold mine is located in Enga Province, about 600km north west of Port Moresby. The mine is operated by a joint venture between Placer Dome (75%), Orogen Minerals Ltd (20%) and Mineral Resources Porgera Pty. Ltd (5%), the latter two representing the state of PNG and local landowners. In early 2006, Barrick Gold Corp acquired Placer Dome in a US$10.4bn takeover, thereby acquiring its interest in Porgera, in which Placer had increased its own holding from 50% during 2002 following its take-over of Aurion Gold Ltd. Porgera was initially an underground operation, with open-pit mining becoming increasingly important from 1993 onwards. Underground production ceased in 1997, but was resumed in 2002. In 2005, 11% of the mine’s output came from underground, with the remainder sourced from open pits and low-grade ore stockpiles. Using an additional secondary crusher and treating higher ore grades, Porgera upped gold output by 20% in 2004, producing 1.02Moz at a cash cost of US$192/oz. However, its output fell again to 835,000oz in 2005, with open-pittable resources nearing depletion. For the remaining life of the mine, production will be obtained from residual underground resources and from stockpiled low-grade ore. GEOLOGY AND RESERVES Mineralisation occurs along the margins of the Porgera intrusive bodies. The Porgera Zone VII orebody is an epithermal style orebody hosted within thermally metamorphosed sediments of the cretaceous. The four precious metal associations are: auriferous pyrite, sphalerite and galena; coarse euhedral auriferous pyrite; fine anhedral auriferous arsenical pyrite; gold and electrum. The majority of gold occurs as submicroscopic gold associated with pyrite. As of December 2004, proven and probable reserves totalled 58.37Mt grading 3.9g/t and containing 7.31Moz of gold, plus measured and indicated mineralisation containing a further 3.16Moz. Exploration by the joint venture continues to identify medium and low grade extensions to the north of the Main Zone. MINING "In 2005, 11% of the mine’s output came from underground, with the remainder sourced from open pits and low-grade ore stockpiles." The open pit has been mined in five stages, with final-stage overburden removal taking place during 2001. Ore is currently mined in the Stage 5 pit, as well as from underground. The open-pit truck and shovel fleet was expanded in 1995, with an O&K RH200 shovel and five Caterpillar 789 trucks. It was again expanded in 1997 to increase production rates from 150,000t/day to 210,000t/day. The mine now handles more than 210,000t/day of ore and waste, with a target supply to the mill of 17,700t/day of ore. Material-handling requirements in 2005 totalled 6Mt of ore and waste. ORE PROCESSING Run-of-mine ore is crushed and ground, free gold is recovered in a gravity circuit and flotation is used to recover a sulphide concentrate. This is then oxidised using autoclaves, producing feed for conventional carbon-in-pulp cyanide leaching to recover the contained gold. Low-grade stockpile and open pit ore are crushed using a gyratory crusher. Coarse ore is conveyed from the stockpile to two parallel SAG mills. The discharge is pumped to three clusters of cyclones in closed circuit with three ball mills. Coarse SAG mill discharge is crushed in two cone crushers and returned to the SAG feed. The slurry is then pumped to the flotation circuit. A Knelson concentrator gravity separation circuit, installed in 1997, has improved recovery of free gold prior to flotation. Flotation concentrates, thickened to 50% solids, form the feed for the oxidation process. Autoclave feed is pumped through three closed stainless steel carbonate reaction tanks in series, the concentrate being mixed with recycled oxidised slurry. The autoclaves operate at 1,725kPa pressure and 197°C, producing feed for the leaching and CIP circuits. Combined leach and CIP recovery is 90–95% of the contained gold. In 1999, a floatation expansion was installed and additional oxygen capacity was added to increase autoclave throughput. GOLD RECOVERY Thickener overflow is percolated upwards through one of two series of five carbon columns, each containing a static bed of 1.5t of activated carbon. Recovery of gold from solution exceeds 99%. The elusion (ion exchange) circuit consists of two pressurised vessels each holding 10t of carbon. Pregnant carbon is eluted using 15 bed volumes of eluant at 140°C and 400kPa pressure. 10t/d of carbon are stripped. During electrowinning, gold and silver metal is precipitated on to steel wool. It is then pressure filtered in a plate and frame press. The resultant 'cake' is smelted in a 1,000kg induction furnace to produce bars of doré bullion averaging 88% gold. From : Mining-Technology.com		The open-pit mine at Pergora. Porgera is located in Enga Province about 600km north west of Port Moresby.
		Cross-section of underground deposits.
		The open-pit truck and shovel fleet was expanded with larger equipment in October 1995 to increase production rates.
		The plant at Pergora. Mineralisation occurs within the Porgera intrusive complex.
		The mill flowsheet. Low-grade stockpile ore and open-pit ore are crushed using a 1,067mm gyratory crusher.

Kaltim Prima Coal Mine, Indonesia

Kaltim Prima, one of the new generation of Indonesian thermal coal producers, is located in north-eastern Kalimantan. It is operated by PT Kaltim Prima Coal (KPC), which from the project's inception up to late 2003 was jointly owned by BP and Rio Tinto. The Indonesian government receives a royalty equivalent to 13.5% of the revenue. The operation is self-contained and employs some 2,700 people. Although BP and Rio Tinto's Contract of Work required the companies to divest part of their holding to local interests, up until 2003 no Indonesian purchaser was able to raise the finance needed to buy them out. "PT Bumi is planning further expansion to 30Mt/yr, plus the development of the Bengalon reserve, some 25km from the existing Sangatta operations." In mid-2003, the companies announced the sale of their holdings in KPC to PT Bumi Resources for a cash price of $500m, including assumed debt. PT Bumi Resources already owned PT Arutmin Indonesia, another major Indonesian coal producer, and has interests in oil, natural gas and mining, amongst other commercial sectors. In 2006, PT Bumi announced the sale of all its coal holdings to PT Borneo Lumbung Energi for $3.2bn. However, the deal subsequently failed, although PT Bumi later indicated that it still intends to divest a proportion of its holdings. PROJECT DEVELOPMENT BP and CRA (now Rio Tinto) successfully tendered for a 7,900km² licence area in eastern Kalimantan in 1978. Exploration from 1982–86 indicated reserves of 112Mt of export-quality thermal coal. Construction began in 1989 and the mine was commissioned in 1991 as a 7Mt/y operation at a cost of $570m. The mine has subsequently been expanded, with a sales target of 20Mt/yr by 2005. PT Bumi is planning further expansion to 30Mt/yr, plus the development of the Bengalon reserve, some 25km from the existing Sangatta operations. In mid-2004, PT Bumi awarded the Australian contractor, Henry Walker Eltin, a $1.2bn, ten-year contract for infrastructure development and mining services at Bengalon, which will have a 6Mt/yr initial capacity. GEOLOGY AND COAL QUALITY Pressure and heat associated with an igneous intrusion has increased the rank at Kaltim Prima to high-volatile bituminous coal. A total of 13 seams range in thickness from 1m to 15m; typically in the range of 2.4m to 6.5m. Seam dips vary from 3° to 20° at the outcrop. The seams are very clean in terms of mineral matter and sulphur and, at 4–8% in some areas, the in-situ moisture content is low. As of the end of 2005, PT Bumi cited reserves at Sangatta at 621Mt, plus 165Mt at Bengalon. The company also has measured and indicated resources of some 3,700Mt. As of mid-2004, PT Bumi cited reserves at Sangatta at 462Mt, plus 157Mt at Bengalon. The company also has measured and indicated resources of some 2,200Mt. The operation produces two main export products. Prima Coal is a high-volatile bituminous steam coal with high calorific value, very low ash, low sulphur and low total moisture. Pinang Coal is similar but has a higher moisture content. Quality parameters are: Product Prima Coal Pinang Coal Moisture (total) 9.5% 14% Ash 4% 6% Volatiles 39% 39% Fixed carbon 52% 46% Total sulphur 0.5% 0.5% Heating value (adb) 30.1MJ/kg 27.6MJ/kg Heating value (gar) 28.5MJ/kg 26.0MJ/kg adb = air-dried basis gar = gross, as received KPC blends run-of-mine coal from its various pits to ensure product consistency. As of end-2001, Kaltim Prima had mineable reserves totalling 462Mt, plus measured and indicated resources of nearly 2,200Mt. MINING TECHNOLOGY KPC operates six to 12 individual open pits at any time, the average stripping ratio being 7.5bcm (bank cubic metres) of overburden per tonne of coal. The overburden material degrades quickly on exposure to the atmosphere and generally provides easy digging. Some overburden rock requires blasting to ensure adequate fragmentation for the shovels. KPC carries out its own mining in most of the pits, but also contracts out a smaller proportion of its mining requirements. "With selective mining, over 90% of the run-of-mine coal only needs crushing and blending to give export-quality Prima Coal." The mine's loading fleet consists of over 20 large hydraulic shovels and backhoes with bucket capacities of up to 34m³. Leading suppliers include Hitachi, with nine EX3500 machines and six EX1800s, and Liebherr, which has six R996 Litronic shovels/backhoes on site. Overburden haulage involves a fleet of 137 trucks, including Caterpillar 785s and 789Bs with capacities of 135–185t, Cat 777s (85t) and Komatsu HD785s (also 85t). Truck scheduling is carried out using a GPS-based Mincom dispatch and management system. COAL PROCESSING With selective mining, over 90% of the run-of-mine coal only needs crushing and blending to give export-quality Prima Coal. Coal from the seam roofs and floors contains more mineral material, and so has to be washed. This 'dirty Prima' and Pinang material is handled separately from the 'clean Prima', with individual streams for the different raw materials. After crushing to –50mm in Gundlach rolls crushers, the washing plant uses dense medium cyclones for 0.5mm to 50mm feed, and spirals for the –0.5mm material, products being dewatered in centrifuges before blending into the Prima Coal stockpile. OVERLAND TO THE PORT The mine site contains separate stockpiles for the Prima and Pinang products, holding 60,000t and 35,000t respectively. Coal is reclaimed and transported by a 13km-long, 2,100t/h-capacity overland conveyor to Kaltim Prima’s dedicated port facilities at Tanjung Bara. Further stockpiles hold a live capacity of 350,000t of Prima and 150,000t of Pinang coals. Coal is transferred directly from mine to ship whenever possible. Vessels of up to 220,000dwt can be handled by the port, with loading facilities at the end of a 2km-long jetty. Twin quadrant loaders can each handle up to 4,700t/h, the normal loading throughput. PRODUCTION Since production began in 1992, Kaltim Prima has increased its output year-on-year, from 7.3Mt in its first year to some 17Mt in 2002 and 2003. PT Bumi is now expanding the Sangatta operation to 30Mt/yr, with a further 6Mt/yr to come from Bengalon. The operation produced 27.6Mt in 2005, with a target for 2006 of 36Mt of coal and some 700Mt of overburden. From : Mining - Technology.com		Kaltim Prima is one of the major export coal mines developed in Kalimantan, Indonesia, over the last ten years.
		Thick, regular seams make for straightforward mining conditions.
		One of the mine’s Hitachi hydraulic excavators, working with Cat hauler.
		Kaltim Prima has six Liebherr R996 Litronic excavators, used with Cat 789B haulers for overburden removal.
		Five of the mine’s fleet of Caterpillar 789B haulers. Truck scheduling is carried out using a Mincom dispatch and management system, based on a global positioning system (GPS) to locate and track individual vehicle movements.
		A luffing and slewing stacker (foreground) and a bucket-wheel stacker-reclaimer (behind) at Kaltim Prima’s port stockpile.
		One of the two quadrant shiploaders which together can load bulk carriers of up to 180,000dwt at 4,200t/h.

Cannington Silver and Lead Mine, Queensland, Australia

he Cannington silver mine is located in north-west Queensland, 200km south east of Mount Isa, near the township of McKinlay. The deposit was discovered by BHP Minerals in 1990 and the mine was commissioned in 1997 at a cost of some AUS$450m. Full production was achieved in early 1999, since when capacity has been expanded from 1.5Mt/y of ore to over 3Mt/y. Cannington is the world's largest single silver producer, representing about 6% of the world's primary silver production, while its lead production represents about 7% of the world's primary lead output. The lead concentrate contains 70% lead and over 3,000g/t silver with low levels of impurities. Long-term contracts for concentrate sales have been agreed with Pasminco (now Zinifex) in Australia, Metaleurop in France, Berzelius in Germany, and various smelters in Japan and Korea Zinc. GEOLOGY AND RESERVES Cannington lies in the south-east corner of the proterozoic Mount Isa Block, within the metamorphics of the lower middle proterozoic eastern succession and overlain by 60m of younger sediments. It is divided by faulting into a shallow, low-grade Northern Zone and a deeper, higher grade Southern Zone. Initial mining will be undertaken in the Southern Zone. Cannington’s major economic sulphides are galena and sphalerite. The silver occurs mainly as freibergite but is also present in solid solution within galena. At the end of 2005, the orebody contained proved sulphide ore reserves of 18.0Mt grading 477g/t silver, 10.7% lead and 3.9% zinc. Measured resources totalled 2.3Mt at 536g/t Ag, 11.94% Pb and 4.49% Zn. The metallurgical recovery rates for zinc, lead and silver were 66%, 88% and 84% respectively. MINING METHOD Cannington is an underground mine accessed via a 5,250m-long, 5.2m-high by 5.5m-wide decline. The main, thicker hanging-wall orebodies of the deposit are mined by transverse, longhole open sloping. "Full production was achieved in early 1999, since when capacity has been expanded from 1.5Mt/y of ore to over 3Mt/y." During the first year of production, a vertical hoisting shaft with a finished internal diameter of 5.6m was constructed from the surface to 650m for ore haulage. The excavation method involves stripping out a 1.8m-diameter raise-drilled pilot hole and lining with concrete from the surface. The shaft is equipped with a tower-mounted friction winder and two 9t skips in counterbalance running on rope guides. The skips are hoisted from a loading station on the 610m level and reach a final hoisting speed of 12m/s. On the surface, tipping scrolls in the shaft headframe tip the skips into a surface bin for transfer to the mill’s stockpile. PROCESSING Processing steps used to produce the lead and zinc concentrates include comminution, flotation, leaching and dewatering. Waste water is pumped to a tailings dam with the flotation overflow. The overflow from the lead concentrate thickener is recycled to the lead flotation circuit. The operation of the concentrator is automated with progammable logic controllers (PLCs), an online sample analyser being used to provide continuous assays on a number of the concentrator streams for silver, lead and zinc. The silver is leached from the lead and zinc concentrates before smelting. PRODUCTION During the year ending June 2006, Cannington mined 3.1Mt of ore grading 461g/t silver, 10.3% lead, and 3.7% zinc. Payable metal production was 38.45Moz of silver, 266,321t of lead and 68,779t of zinc. EXPANSION BHP Billiton has been implementing its Cannington Growth project since 2003, with the aim of improving recoveries, bringing the Northern Zone orebody into production and sustaining ore production at a rate of 2.4Mt/y. TRANSPORT, STORAGE AND EXPORT After dewatering, the lead and zinc concentrates are stored in a 10,000t-capacity storage shed before being loaded into 118t-capacity side-tipping, covered trailer roadtrains by a front-end loader for transport to Cannington's storage and rail loading facilities at Yurbi on the Matilda Highway. Supplied by Roaduser Research, the three 53.5m-long Icon roadtrains carry eight covered bins mounted on six trailers, loading and unloading taking about 20 minutes at each end of the journey. The concentrates are stored separately in an 8,000t-capacity shed at Yurbi prior to loading into rail wagons. Queensland Rail has supplied 50 new 63t-capacity wagons for transporting the concentrates to the port of Townsville for export to world markets. From : Mining- Technology.com		When in full production, Cannington will become the world's largest single silver producer, representing about 6% of the world's primary silver production.
		The Cannington mine is located in north-west Queensland (Australia), 200km south east of Mount Isa, near the township of McKinlay.
		The hoisting shaft head frame. The excavation method involves stripping out a 1.8m-diameter raise drilled pilot hole and installing a concrete lining working down from the surface.
		Boxcut development at the start of the decline back in 1993.
		Processing plan layout schematic. Waste water will be pumped to a tailings dam with the overflow.
		Metroliner landing at Cannington.