Platinum September 2009

Definition, mineralogy and Pt Pd Rh Ir Ru Os Au nt Atomic 195.08 106.42 102.91 192.22 101.07 190.23 196.97 deposits weight opme

vel Atomic Definition and characteristics 78 46 45 77 44 76 79 de number l Platinum (Pt) is one of a group of six chemical elements ra UK collectively referred to as the platinum-group elements Density

ne 21.45 12.02 12.41 22.65 12.45 22.61 19.3 (gcm-3) mi (PGE). The other PGE are palladium (Pd), iridium (Ir), osmium e Melting bl (Os), rhodium (Rh) and ruthenium (Ru). Reference is also 1769 1554 1960 2443 2310 3050 1064

na point (ºC)

ai commonly made to platinum-group metals and to platinum- Electrical st group minerals, both often abbreviated to PGM. In this su resistivity r document we use PGM to refer to platinum-group minerals. 9.85 9.93 4.33 4.71 6.8 8.12 2.15

f o (micro-ohm

re cm at 0º C) nt Chemically the PGE are all very similar, but their physical Hardness Ce Minerals 4-4.5 4.75 5.5 6.5 6.5 7 2.5-3 properties vary considerably (Table 1). Platinum, iridium (Mohs) and osmium are the densest known metals, being significantly denser than gold. Platinum and palladium are Table 1 Selected properties of the six platinum-group highly resistant to heat and to corrosion, and are soft and elements (PGE) compared with gold (Au). ductile. Rhodium and iridium are more difficult to work, while ruthenium and osmium are hard, brittle and almost pentlandite, or in PGE-bearing accessory minerals (PGM). unworkable. All PGE, commonly alloyed with one another Cabri (2002) provide mineralogical and chemical data for or with other metals, can act as catalysts1 which are more than 100 different PGM. Many others have been exploited in wide range of industrial applications. Platinum reported but most of these are poorly characterised and palladium are of major commercial significance, while, on account of their rarity and their occurrence in very of the other PGE, rhodium is the next most important. fine grains, commonly only a few microns in size. It is Iridium and ruthenium are traded in small quantities significant to note that some PGM are known only from for use chiefly in catalysts and electronic applications. one deposit and that there may be considerable variation Osmium metal is little used because in powdered form it produces a toxic gas when exposed to air.

The PGE are very rare in the earth’s crust. The abundance of platinum and palladium in the crust are similar, approximately 5 parts per billion (ppb), by weight. Rhodium, iridium and ruthenium are even scarcer at about 1 ppb. Relative to other rock types in the crust the PGE are enriched in ultramafic2 lithologies, such as peridotite3, in which platinum and palladium concentrations are commonly 10–20 ppb.

Mineralogy In nature the PGE are chiefly held either in base-metal sulphide minerals, such as pyrrhotite, chalcopyrite and

Unless otherwise stated, copyright of materials contained in this report are vested in NERC. Placer platinum nugget from the Choco River, Colombia. BGS © NERC 2009. All rights reserved. © Museo regionale di Scienze Naturali di Torino. Mineral profile

1 Catalysts are substances that cause or accelerate chemical reactions without themselves being affected. 2 Ultramafic: composed chiefly of ferromagnesian (Fe-Mg) minerals, such as olivine and pyroxene. 3 Peridotite: a class of ultramafic rocks consisting of predominantly olivine, with or without other ferromagnesian (Fe-Mg) minerals. 2 Platinum 8 7 6 feldspathoid minerals. 5 4 A varietyofotherdeposittypes resultingfromdifferent which thePGEoccurinassociationwithsulphide-richores. mineralisation; andnickel-coppersulphidedepositsin which areassociatedwithsparse,dispersedsulphide of twoprincipaltypes(Table 3): PGE-dominantdeposits or ultramaficigneousrocks.Magmatic temperature magmaticprocessesandarefoundinmafic shown inFigure1.Mostdepositsareformedbyhigh platinum occurrences,deposits,minesanddistrictsis copper. Amapshowingthedistributionofselected of severaltypes,commonlyassociatedwithnickeland settings andaccordinglyPGEarederivedfromdeposits Enrichment ofPGEoccursinawidevarietygeological Major depositclasses more commonPGMarelistedinTable 2. arsenic, antimony, telluriumandselenium.Someofthe PGE arebondedtoavarietyofligands with tin,copper, lead,mercuryandsilver. InotherPGMthe or withothermetals,notablyiron,andlesscommonly commonly formawidevarietyofalloyswithoneanother The PGErarelyoccurinnatureasnativemetalbutmore a depositordistrict. in theabundanceandproportionsofindividualPGEwithin Table 2Aselectionofthemorecommonplatinum-groupminerals (PGM). Immiscible: referring toliquidsnotablebemixedtogether. Differentiation: thechange inthecompositionofmagmadue tothecrystallisationofminerals settlingatthebottom ofamagmachamber. Magmatic: relatingto moltenmaterialbeneathorwithinthe earth’s crust, fromwhichigneousrockisformed. Mafic: composedofoneormoreferromagnesian (iron-magnesium),dark-colouredminerals, such asolivineandpyroxene,incombinationwithquartz,feldsparor Ligand: amolecule,ion,oratomthatisbonded tothecentralmetalatomofacoordination compound. Sulphides Alloys Group

Ruarsite Laurite Hollingworthite Erlichmanite Cooperite Braggite Tulameenite Rustenburgite Osmiridium Isoferroplatinum Atokite Name Potarite 4 6 includingsulphur, PGEdepositsare (Ru,Os)AsS (Ru,Os)S RhAsS OsS PtS (Pt, Pd)S Pt (Pt,Pd) PdHg OsIr Pt (Pd,Pt) Formula 2 3 FeCu Fe 2 3 3 Sn Sn 2 5

Bismuthides Antimonides Arsenides Group rocks were sourced. were rocks host mafic-ultramafic the where mantle the from derived been have to believed are PGE the and accepted widely is liquid sulphide a by collection PGE of importance the understood, well not are deposits these of genesis the for responsible processes the Although chalcopyrite. and pentlandite pyrrhotite, chiefly sulphides, cent) per volume 5 to (up disseminated sparsely from derived copper and Ni by-product minor with components economic main the are PGE the deposits these In PGE-dominant deposits quantities ataparticularlocation. this PGE-enrichedsulphideliquidaccumulatesinsufficient sulphide liquid.Anoredepositmaysubsequentlyformif silicate magmaleadingtotheirextremeenrichmentinthis acts likeaspongescavengingthePGEfromcoexisting the magmaasdisseminateddroplets.Thissulphideliquid sulphur andanimmiscible and concentration.Themagmabecomessaturatedwith magmatic processesofcrystallisation,differentiation In simpletermsPGE-sulphidedepositsarederivedfrom significance intermsofPGEproduction(Table 4). processes arealsoknownbuttheseofrelativelyminor Tellurides

Moncheite Michenerite Merenskyite Kotulskite Froodite Geversite Sudburyite Stibiopalladinite Isomertieite Genkinite Stillwaterite Sperrylite Name 8 sulphideliquidseparatesfrom www.MineralsUK.com (Pt,Pd)(Te,Bi) Pd(Bi,Sb)Te (Pd,Pt)(Te,Bi) PdTe PdBi Pt(Sb,Bi) (Pd,Ni)Sb Pd Pd (Pt,Pd,Rh) Pd PtAs Formula 5 11 8 Sb As As 2 2 2 3 2 Sb 2 4 2 Sb 2 2 3 7

3 Platinum

Noril’sk- Pechenga Talnakh Skaergaard District Sukhoi Log Muskox Inagli Ust-Belaya Goodnews Ungava Keivitsa intrusion Thompson Bay Unst Portimo Udokan Seniav Penikat Mikailovskoe Urals Srednefersinskoe Lac des Iles Stillwater Kondyor Kvinum Sudbury Yastrebovskoe Zyranovskoe Kempirsai Tulameen Kupferschiefer Complex East Bull Lake Duluth Skouries Ojut Tolgoi New Kadzharan Rambler N Jinchuan Dali Nuasahi

Zambales Freetown Yubdo Cerro La Pinto Choco River Platina Pedro Branca Creek Coronation Serra Caraiba Hill Pelada Jacare Great Dyke Radio Hill Sally Malay Itabire (Jacutinga) Stella Munni Pacajake Rincon del Tigre Munni Musgrave Intrusion Palabora

PGE Ni-Cu Others Bushveld dominant dominant Complex Kambalda www.MineralsUK.com (Merensky Reef+Platreef) District PGE mines/ mining districts Southland

Other deposits/ occurences

Figure 1 The distribution of selected PGE mining districts, mines, deposits and occurrences. Deposit type Brief description Typical grades Major examples PGE-dominant Merensky type Extensive, laterally continuous, thin 5–7 g/t Pt+Pd; Pt/Pd9 = 3 Merensky Reef, Bush- layer, or ‘reefs’, of ultramafic rocks with in Merensky Reef. Major veld Complex, South minor disseminated nickel and cop- source of Pt, Pd and Rh. Africa; Great Dyke, per sulphides. Formed in large layered Zimbabwe; J-M Reef, mafic-ultramafic complexes by magmatic Stillwater Complex, processes. USA; Munni Munni Complex, Western Australia. Chromitite type10 Similar to Merensky type but comprising 4–8 g/t Pt+Pd; Rh 0.3–0.6 UG2, South Africa; thin layers of massive chromite11 with g/t in UG2. Pt/Pd = 2.5 in Lower Chromitites, very sparse base metal sulphide miner- UG2. Major source of Pt, Stillwater Complex, als. Pd and Rh. USA. Contact type Extensive zones (km) of discontinuous 1–4 g/t Pt+Pd in Platreef, Platreef, Bushveld PGE mineralisation with low-grade with Pt/Pd ca. 1; by-product Complex; Duluth nickel and copper in heterogeneous Ni and Cu. Major PGE Complex, USA; Lac des basal contact zones of layered intrusions. resources. Iles, Canada; East Bull Commonly heterogeneous, brecciated12, Lake, Canada; Portimo, xenolithic13. Finland. Dunite pipes High grade platinum mineralisation in 3 g/t to 2000 g/t. No longer Onverwacht, Driekop discordant pipe-like14 bodies of dunite, up mined. and Mooihoek, Bush- to 1 km in diameter. Largely worked out. veld Complex, South Africa. Nickel-copper-dominant (with by-product PGE) Associated with Ni-Cu sulphide deposits in impact melt 1–10 g/t Pt+Pd. Numerous Sudbury, Canada. meteorite impact rocks and underlying radial and concen- deposits worked mostly for tric fracture and breccia zones15. Ni, with lesser Cu and PGE. Related to rift- Ni-Cu sulphide deposits in sub-volcanic 2–100 g/t PGE. Average Jinchuan, China. and continental- sills which feed flood basalts16 associated 7.31 g/t Pd and 1.84 g/t Pt flood basalts with intercontinental rifting. in Noril’sk, Russia. Komatiite related Nickel sulphide deposits related to Commonly a few hundred Kambalda, Western komatiitic17 (MgO-rich) volcanic and intru- ppb, locally greater than 1 g/t. Australia; Pechenga sive rocks of Archaean18 and Palaeoprot- Pt/Pd generally <1. district, Russia; Thomp- erozoic19 age. son Belt, Canada; Ungava Belt, Quebec, Canada.

Table 3 Key characteristics and examples of the major PGE deposit types.

9 Platinum to palladium expressed as a ratio. 10 Chromitite: an igneous cumulate rock composed chiefly of the mineral chromite. 11 Chromite: an iron magnesium chromium oxide belonging to the spinel group. 12 Brecciated: a rock that has been mechanically, hydraulically or pneumatically broken into angular fragments and re-cemented. 13 Xenolithic: containing xenoliths (discrete and recognisable fragments of country rock in an igneous intrusion). 14 Discordant pipe-like: a cross-cutting vertical to sub vertical igneous intrusion. 15 Breccia zones: areas containing abundant fragmented and broken rocks, in this case caused by an impact event. 16 Flood basalts: a series of thick basalt deposits covering extensive areas of land or ocean floor resulting from a very large scale volcanic eruption or series of eruptions. 17 Komatiitic: relating to an ultramafic mantle-derived volcanic rock with low SiO2, low K2O, low Al2O3 and high to extremely high MgO. Platinum 18 Archaean: the period of geological time that is older than 2500 million years ago. 19 Palaeoproterozoic: the period of geological time from 1600 to 2500 million years ago. 4 www.MineralsUK.com Four classes of PGE-dominant deposits are recognised: within part of the complex known as the Critical Zone which comprises packages, or cyclic units, of repetitively • Merensky Reef type layered chromitite, pyroxenite, norite and anorthosite on a • chromitite reef type scale of centimetres to tens of metres. • contact type • dunite pipes Platinum is currently mined from three horizons in the All of these are typically developed in the Bushveld Bushveld Complex: the Merensky Reef, the UG2 Reef, and the Complex in South Africa, which is the largest layered Platreef. The Merensky and the UG2 are extensively worked igneous complex in the world. by both open pit and underground mining methods on the Eastern and Western Limbs. The Merensky Reef has been Bushveld Complex exploited for PGE for many years with production starting in The Bushveld Complex hosts about 90 per cent of all 1928 in the Rustenburg area. The UG2 Reef was not mined known platinum resources in the world and accounts for on a commercial scale until 1985 on account of metallurgical more than 80 per cent of global platinum production. It problems related to the high chrome and low sulphide covers an area of approximately 66 000 km2 and is about contents. At present, however, the UG2 is worked at several 9 km thick (Figure 2). The Bushveld Complex is divided localities and accounts for a significant percentage of annual into three main sectors: the Western Limb, the Eastern PGE production from the Bushveld. The Platreef is restricted to Limb and the Northern Limb. It is saucer-shaped with the Northern Limb of the complex where mining commenced the layered mafic and ultramafic rocks dipping into the in 1926 but lasted only a few years. Recent increased demand centre of the intrusion where they are covered by felsic20 and associated high prices has led to considerable exploration lithologies. The platinum-bearing horizons are located on the Platreef since 2000.

Platinum Figure 2 The geology of the Bushveld Complex showing the location of platinum mines and advanced projects.

20 Felsic: a rock consisting chiefly of feldspars, feldspathoids, quartz, and other light-coloured minerals. 5 www.MineralsUK.com Merensky Reef type generally regarded as the largest PGE resource in the world. The Merensky Reef is the type example of a PGE- The ruthenium and rhodium content of the UG2 (c. 15 per dominant deposit without significant associated sulphide cent and c. 8.7 per cent of total PGE content, respectively) mineralisation. Other important examples are found in is also significantly higher than the Merensky Reef (c. 6.2 the Great Dyke, Zimbabwe and the Stillwater Complex, per cent and c. 2.9 per cent), and hence it is an important USA. This class is a major source of global production of source of these rare but useful metals (Lonmin, 2009). The platinum and palladium. UG2 comprises a chromite layer between 0.7 and 1.3 m in thickness with included sparse disseminated sulphide These deposits occur as thin, laterally extensive, mineralisation. It is closely associated with a 0.5 m thick stratiform21 zones of sparsely disseminated sulphides pegmatoidal pyroxenite cumulate24. The UG2 has a similar within major layered mafic-ultramafic igneous intrusions. lateral extent to the Merensky Reef, occurring below it at In the Bushveld Complex these deposits are typically depths from 30 m up to about 400 m. The average grade located about 2 km above the base of the intrusion. There of the UG2 varies from approximately 4 to 8 g/t Pt+Pd. The is no consensus on the processes responsible for their PGMs in the UG2 comprise mainly sulphides and alloys, genesis but the most widely accepted model involves including laurite, cooperite, braggite and Pt-Fe alloy. mixing of a residual magma after partial crystallisation with a new pulse of magma leading to sulphide saturation Platreef and separation of immiscible sulphide droplets which The Platreef is a layer of ultramafic rocks, chiefly pyroxenite, scavenge PGE from the silicate magma (Lee, 1996). situated along the base of the Northern Limb of the Bushveld Complex. Like the Merensky and UG2 reefs it can The Merensky Reef comprises a pegmatoidal22 pyroxenite be traced for tens of kilometres. However, it is far thicker layer about 1 m thick, bounded on both sides by thin (up to 300 m) than the Merensky and UG2 horizons and has chromitite layers and containing up to 3 per cent generally higher base metal contents, particularly nickel disseminated sulphides. It can be traced laterally for many and copper, up to about 3 volume per cent. The Platreef hundreds of kilometres and is found on both the Eastern and is a major PGE resource with mineralisation in both the Western limbs of the Bushveld Complex. The grade of the pyroxenite and sections of the immediate footwall rocks. Merensky Reef averages about 5–7 g/t Pt+Pd (Maier, 2005), The mineralisation is 10–30 m thick and is best developed although the mineralogy is quite variable and includes a along a 25 km section of strike length. It varies considerably wide range of alloys, sulphides, tellurides and arsenides. within this interval, in part according to the nature of the footwall rocks which include extensive sections of dolomite, granite, banded iron formation, chert, quartzite and shale. In places the magma has melted and reacted with the footwall giving rise to cross-cutting granitic rocks and widespread xenoliths of dolomite and calc-silicate25 rocks. The mineralisation in the Platreef is less laterally continuous than the reef styles and is sporadically developed within these heterogeneous lithological packages. The PGE contents are also generally lower than in the reefs, typically in the range 1–4 g/t. The PGE mineralogy of the Platreef is dominated by sulphides, tellurides and arsenides, but this varies significantly both laterally and vertically.

The PGE-dominant mineralisation in the Platreef may be classified as contact-type PGE mineralisation, which are Merensky Reef ore. Scale bar is 50 mm. basal accumulations of magmatic sulphides associated with abundant xenoliths and brecciation, and coarse pegmatitic Chromitite reef type textures. Important examples of this class are recognised The UG2 Reef, one of many thin near-massive23 chromite in the Duluth Complex, Minnesota, USA, the Portimo layers in the Critical Zone of the Bushveld Complex, is Complex in Finland, the Federov Pansky intrusion in the Kola

21 Stratiform: an ore deposit that occurs as a specific stratigraphic horizon. 22 Pegmatoidal: a term describing a very coarse-grained igneous rock characterised by crystals >3 cm in length. 23 Platinum Massive (of a mineral deposit): homogeneous mineralised unit. 24 Cumulate: igneous rock formed by the settling of crystals in a magma chamber. 25 Calc-silicate: a metamorphic rock consisting mainly of calcite and calcium-bearing silicate minerals. 6 www.MineralsUK.com Peninsula of Russia and in the East Bull Lake intrusive suite, significant and contains approximately 80 per cent of the Ontario, Canada, although these deposits are not mined for Great Dyke’s total PGE resources. PGE at present. The Lac des Iles deposit in north-western Ontario, Canada, mined chiefly for palladium between 1993 The Stillwater Complex (2700 Ma) in Montana, USA is and 2008, is similar in some respects to contact-type PGE another of the world’s major layered intrusions that hosts mineralisation. However, certain key features of this class important PGE mineralisation. The complex is divided into are absent and it is best compared with other PGE-dominant a Basal Series, an Ultramafic Series, and a Banded Series. deposits in large layered complexes. The PGE-bearing J-M Reef, which occurs in the Lower Banded Series of norite and gabbronorite, can be traced Dunite pipes for 45 km along strike and approximately 1.6 km down-dip. A fourth style of PGE-bearing mineralisation in the Its vertical depth extent is undefined. The reef consists Bushveld Complex is found in dunite pipes. These are of a 1–3 metre thick pegmatitic peridotite and troctolite discordant pipe-like bodies, up to 1 km in diameter, of containing sparsely disseminated sulphides (0.5–1 volume varying composition. Numerous such bodies are found per cent) and PGM. In contrast to deposits in the Bushveld within the Bushveld Complex, but in only four of them have Complex and the Great Dyke, the J-M Reef is relatively significant PGE mineralisation been discovered. These enriched in palladium with a Pd/Pt ratio of about 3.6. occur in a 20 km belt on the Eastern Limb to the north- The reef contains an average of 20–25 g/t Pd+Pt over a west of Burgersfort. High-grade platinum mineralisation, thickness of about two metres. Most of the palladium is locally up to 2000 g/t Pt, occurs in discrete zones of the contained within pentlandite, while the platinum occurs pipes within unmineralised dunite. Discovered in 1924 mostly in moncheite, braggite, cooperite and Pt-Fe alloy. and largely mined out by 1930, there is little modern The J-M reef is worked from two mines with combined information on these deposits. The main PGE-bearing production of 499 000 oz28 of platinum and palladium in phases were Pt-Fe alloy with subordinate sperrylite, 2008 (Stillwater Mining Company, 2009) hollingworthite and irarsite (IrAsS). The Lac des Iles Intrusive Complex (LDI-IC) (2700 Ma) Other PGE-dominant deposits is a suite of mafic-ultramafic intrusive rocks situated The Great Dyke (2600 Ma26) is a layered mafic-ultramafic approximately 85 km north of Thunder Bay, Ontario, intrusion that can be traced for 550 km in a north-north- Canada. Mineralisation is hosted in the Roby Zone Ore easterly direction across central Zimbabwe. The intrusion, Body in the compositionally and texturally complex Mine which has a width of 4–11 km, was first described in Block Intrusion. 1867, but it was not until 1918 that platinum, together with nickel and copper, was discovered within it. The Open pit mining commenced at Lac des Iles in 1993, Great Dyke is now a world class resource of PGE and also followed by underground operations in 2006. As a result contains major deposits of chromite. of low metal prices the mine was closed at the end of October 2008 and placed on care and maintenance. The Great Dyke developed in a series of up to five initially Approximately 212 000 oz of palladium and 16 000 oz of isolated magma sub-chambers that became linked at platinum were produced in 2008, at an average grade of progressively higher levels as they filled with rising magma. 2.49 g/t Pd (North American Palladium Ltd, 2009). Gold, The lower layered rocks of the Ultramafic Sequence of the copper and nickel are important by-products. intrusion are synclinal27 in cross-section and dip towards the centre of each magma chamber. These zones are overlain Nickel-copper-dominant deposits by a thick sequence of gabbros and norites comprising the Magmatic nickel-copper±PGE deposits are the most Mafic Sequence. The complexes are known, from north important source of nickel worldwide. Copper, cobalt and to south, as Musengezi, Hartley, Selukwe and Wedza. the PGEs, mainly palladium, are important co-products Platinum is associated with two layers within the Ultramafic or by-products. In some deposits gold, silver, chromium, Sequence: a 30–60 m zone of disseminated mineralisation sulphur, selenium, tellurium and lead are also recovered in the Lower Sulphide Zone (LSZ); and a 2–8 m zone of from the ores. PGE-enriched mineralisation in the Main Sulphide Zone (MSZ). Currently only the MSZ is economic to exploit. The The dominant ore minerals are sulphides, pyrrhotite, Hartley Complex is by far the largest and economically most pentlandite and chalcopyrite, which generally constitute

26 Ma: million years ago Platinum 27 Synclinal: relating to a fold in rocks in which the rock layers dip inward from both sides towards the axis. 28 Throughout this publication wherever ‘ounces’ (abbreviated to ‘oz’) are used, this refers to Troy ounces, where one Troy ounce = 31.10 g. 7 www.MineralsUK.com more than 10 per cent by volume of the host rock. Nickel liquid that settled to the lower part of the magma chamber grades typically range from 0.5–3.0 per cent nickel, with on account of its density. As the sulphide droplets attendant copper in the range 0.2–2.0 per cent. PGE segregated, they scavenged chalcophile31 elements such contents vary widely from a few ppb up to, exceptionally, as nickel, copper and PGE. Where these sulphide droplets 10 g/t. The size of the deposits ranges from a few hundred became sufficiently concentrated they may have formed a thousand up to a few tens of million tonnes. Globally two magmatic sulphide deposit, either in a basal or marginal nickel-copper camps are predominant, each containing setting. Particularly favourable sites are the conduits more than 10 million tonnes of nickel metal: Sudbury, through which new magma flowed into the magma chamber. Ontario, Canada and Noril’sk-Talnakh, Russia. Deposits related to meteorite impact Magmatic sulphide deposits occur in diverse geological The nickel-copper-PGE deposits of the Sudbury Igneous settings in rocks ranging in age from Archaean to Permo- Complex (SIC) are the only known examples of this type of Triassic29. They are associated with magmas of various magmatic sulphide deposit the origin of which is attributed types. As a result of this diversity these deposits have to a meteorite impact at 1850 Ma. The impact crater was been classified in several different ways. A relatively originally about 200 km in diameter with the mineralisation simple scheme was proposed by Eckstrand and Hulbert located at the base and in the footwall of the impact melt. (2007) who recognised four principal classes based on the Following later regional deformation the SIC now occupies nature of their host rocks: an elongate basin 65 km long and 27 km wide with rocks along the north flank dipping inwards at about 30° and 1. A meteorite-impact mafic melt with basal sulphide ores. Sudbury is the only known example of this type. those along the south dipping inwards at 45°–60°. The nickel deposits, which are present on both the north and 2. Rift- and continental-flood basalt, with associated dykes and sills. Important examples include the south flanks of the basin, are hosted by a basal mafic Noril’sk-Talnakh district in Russia and Jinchuan, China. noritic unit containing abundant fragmental material, 3. Komatiitic (magnesium-rich) volcanic flows and referred to as the ‘sublayer’. Radiating and concentric related intrusions. Important examples include fracture and breccias zones, known as ‘offsets’, in the Kambalda, Australia, Thompson and Raglan, Canada underlying footwall locally host sulphide-rich orebodies and Pechenga, Russia. enriched in copper and PGE at depths up to 400 m below 4. Other mafic-ultramafic intrusions. Although deposits the sublayer. The sulphide ores have typical magmatic of this class contain significant resources of nickel sulphide mineralogy and textures. A wide range of PGMs and copper, their PGE contents are generally very are present of which the most abundant are tellurides low. The major deposits at Voisey’s Bay in Labrador, (michenerite and moncheite) and arsenides (sperrylite). Canada, are the most important nickel resource in this category, but PGE are not recovered in processing Deposits related to rift- and continental-flood basalts the nickel ores. Accordingly this deposit class is not The Noril’sk–Talnakh region in Russia is the world’s largest considered further in this review. producer of nickel. The ores here are also very rich in PGE and consequently Noril’sk is the world’s largest palladium Despite the diversity of the settings in which they form producer and the second largest platinum producer. nickel-copper sulphide deposits share certain common The resource in the region has been estimated at more features that have allowed a generalised genetic model than 1.3 billion tonnes averaging 1.77% Ni, 3.57% Cu, to be developed. They are produced from olivine-rich, 0.06% Co, 1.84 g/t Pt and 7.31 g/t Pd (Naldrett, 2004). The primitive magmas and are commonly located in proximity Noril’sk Talnakh deposits are associated with the huge to prominent crustal sutures30 that focused ascent of the Permian32 flood basalt suite known as the Siberian Traps, magma allowing transport of their contained metals to which developed in major intra-continental rift zones33. high levels in the crust. Their emplacement in the crust The nickel-copper-PGE ores are hosted by thin (<350 m) was accompanied by contamination with sulphur-bearing gently-dipping sub-volcanic differentiated gabbroic sills. sedimentary rocks (commonly evaporites or carbonaceous The massive sulphide ores occur as flat-lying sheets at the shales) leading to saturation of the magma with sulphur. base of the sills and in the underlying footwall sediments. This resulted in the segregation of an immiscible sulphide Other ore types, mostly stringers34 and disseminations, are

29 Permo-Triassic: the period of geological time from 280 to 205.1 million years ago. 30 Crustal sutures: the area where two continental plates have joined together through continental collision. 31 Chalcophile: elements that have an affinity for sulphur. 32 Permian: the period of geological time from 299 to 251 million years ago. Platinum 33 Rift zones: a large area of the earth in which plates of the earth’s crust are moving away from each other. 34 Stringers: a small vein or seam of ore. 8 www.MineralsUK.com found both within, and at the upper contacts of, the sills. (Barnes, 2004). In northern Quebec, Canada, several basal The most widely accepted model for the genesis of the contact nickel-copper deposits with minor attendant PGE Noril’sk deposits involves the passage of deep, mantle- occur in the Raglan district of the Cape Smith foldbelt and sourced magmas along major faults extending to the base are mined at four sites (Lesher and Keays, 2002). of the crust. Interaction of these magmas with sulphur- bearing sedimentary rocks is believed to have led to Other important nickel mining districts which work sulphur saturation of the magmas and caused precipitation komatiite-associated deposits include the Thompson of nickel and PGE. Nickel Belt of Manitoba, Canada and the Pechenga district of the Kola Peninsula in Russia, close to the border with Another major deposit of this type is Jinchuan in China Norway. Values up to 1.3 g/t Pt and 1.2 g/t Pd have been which contains more than 500 million tonnes of ore reported in the Pechenga ores but values below 1 g/t are grading 1.1 wt% Ni and 0.7 wt% Cu (Su et al., 2008). It more typical of this district (Brugmann et al., 2000). has been mined for nickel and copper since 1964, although in recent years platinum and palladium production has Other deposit types assumed major importance. It currently accounts for Enrichment of PGE to concentrations markedly above about 95 per cent of China’s PGE production. The deposit typical crustal values has been documented in a wide is hosted by the Upper Proterozoic35 Jinchuan Intrusion range of other geological settings. In most cases these are which is located at the northern margin of the elongate, not currently economic to mine using large-scale modern fault-bound Longshoushan thrust belt. The intrusion, techniques, although in the past some have supported about 6.5 km long and 0.5 km wide at surface, comprises small-scale bedrock mining operations. Elsewhere shallow predominantly olivine-rich cumulate rocks and is disposed high-grade deposits are currently worked by mostly small- in a number of en echelon36 fault-bound slices. The ores scale or artisanal operations. are chiefly disseminated and net-textured37 copper-nickel- iron sulphides comprising between 1 and 10 volume per Alaskan or Alaskan-Ural type cent of the rock. The most common PGM are sperrylite, A variety of zoned ultramafic intrusive complexes, referred froodite, michenerite and various Pd-Pt tellurides. to as ‘Alaskan’ or ‘Alaskan-Ural’ type, named after the areas where these deposits were first described, are Deposits related to komatiitic rocks commonly enriched in PGE. These dome- or pipe-shaped Nickel-copper deposits associated with komatiitic bodies are generally small, up to 40 km2, and comprise a volcanic flows and sills are widespread in Archaean and central core of dunite passing outwards to pyroxene-rich Palaeoproterozoic terranes in Australia, Canada, Brazil, units and an outer rim of gabbro. Although many of these Finland and Zimbabwe. Two principal types of ores have complexes contain primary PGE mineralisation, often been recognised: high grade (1.5–4.0 % Ni) massive, associated with chromite, only a few have been mined for breccia and matrix ores occurring in small deposits, up to PGE e.g. the Nizhny Tagil Complex in the Urals, which was a few million tonnes, at the basal contacts of ultramafic worked until 1935. flows and sills; and large (up to 500 million tonnes), low grade (0.6% Ni) deposits comprising disseminated Other deposits of this type are found in British Columbia, sulphide internal lenticular zones. Both types are found in Alaska, Koryakia in north-east Russia and in the Kondyor the Norseman–Wiluna Greenstone Belt of the Archaean intrusion in the Siberian Platform. These locations are, Yilgarn Craton of Western Australia and have been mined however, best known for the important platinum-rich at many localities. alluvial placer deposits derived from their erosion and which have supported mining operations for more than a Basal contact massive sulphide deposits are exemplified hundred years. by deposits in the Kambalda district. The type example is Mount Keith, which is a large tonnage, disseminated Placers deposit. Palladium and platinum are by-products of nickel Alluvial placer deposits are concentrations of heavy mining in this belt although the PGE content of these ores minerals transported and deposited with sand and gravel is relatively low. Values in the range 0.1 g/t Pt and 0.1–0.5 by rivers. Dense platinum-bearing mineral grains are g/t Pd have been reported for nickel sulphide ores of the concentrated at certain sites from where they may be Black Swan area, about 70 km north-east of Kalgoorlie extracted by shallow excavation and/or dredging. Placer

35 Proterozoic: the period of geological time from 2500 to 542 million years ago. Platinum 36 En echelon: parallel or sub-parallel, closely-spaced, overlapping or step-like structural features in rock. 37 Net-textured: a network of sulphides within a rock. 9 www.MineralsUK.com Deposit type Brief description Typical grades Major examples Alaskan or Alaskan- PGE enrichment in small zoned Generally low grade, but with Nizhny Tagil, Urals; Tulameen Ural type ultramafic complexes. Primary local extreme enrichment. Complex, Canada. mineralisation mined at a few localities. Placer type An accumulation of dense PGM Generally low grades with Urals, Russia; Choco River, in sand and gravel deposits laid sporadic rich pockets. Colombia; Goodnews Bay, down in a river system. Alaska; Southland, New Zealand. Ophiolites PGE enrichment chiefly with Values in g/t range reported Unst, UK; Zambales, Phillip- podiform38 chromitite deposits from Unst. pines; Kempirsai, Russia; Al in lower sections of ophiolite39 Ays, Saudi Arabia. complexes. Later hydrothermal40 enrichment may upgrade PGE contents. Laterites Residual enrichment of PGE 0.5 g/t Pt. Yubdo, Ethiopia. caused by intense tropical weathering of ultramafic rocks. Veins Polymetallic41 veins and/or Tens of g/t Pt+Pd. Hundreds New Rambler, USA; Water- hydrothermal remobilisation of g/t at Waterberg. berg, South Africa; Rathbun of nickel, copper and PGE in Lake, Canada. mafic-ultramafic rocks with re-deposition of PGE along shear zones42. Unconformity-related Hydrothermal PGE enrichment 0.19 g/t Pt, 0.65 g/t Pd, 4.31 g/t Coronation Hill, Australia; with gold ± uranium in metased- Au at Coronation Hill (Carville Serra Pelada, Brazil. imentary43 rocks at or close to et al., 1990). Tens/hundreds g/t an unconformity44 with younger, Pt and Pd at Serra Pelada. oxidised sedimentary rocks. Commonly focused along faults. Porphyry deposits Local PGE enrichment with gold Generally less than 1 g/t PGE. Elatsite, Bulgaria; Skouries, in porphyry45 style copper depos- 0.16 g/t Pd, 0.038 g/t Pd from Greece; Aksug, Russia; Santo its hosted by igneous intrusions. Santo Tomas. Tomas II, Phililppines. Shales and other PGE enrichments in metallifer- Generally < 1 g/t, but local Kupferschiefer, Poland; Yukon, sedimentary rocks ous black shales. Generally thin very high values in the Kup- Canada; Sukhoi Log, Siberia. but may be laterally extensive. ferschiefer. Carbonatite and alkaline PGE enrichment in small Few hundred ppb in Palabora; Palabora, South Africa; Catalão complexes carbonatite-phoscorite igne- few g/t in Brazilian exam- and Ipanema, Brazil; Kovdor, ous complexes. Disseminated ples. 0.76 g/t Pd, 0.23 g/t Pt Russia. Coldwell Complex, copper-palladium-rich sulphide and 0.27% Cu in Marathon Canada; Marathon, Canada. mineralisation in gabbro at deposit. Coldwell.

Table 4 Key characteristics and examples of other PGE deposit types.

38 Podiform: an elongate lenticular or rod-like shaped orebody. 39 Ophiolite: a section of the earth’s oceanic crust and the underlying upper mantle that has been uplifted or emplaced to be exposed within continental crust. 40 Hydrothermal: related to processes involving heat and water. 41 Polymetallic: a rock composed of a combination of different metals. 42 Shear zones: microscopic to regional-scale domains across which deformation and/or displacement has occurred. 43 Metasedimentary rock: a sedimentary rock that shows evidence of having been subjected to metamorphism. 44 Unconformity: a surface of erosion or non-deposition representing a gap in the geological record. Platinum 45 Porphyry : a mineral deposit comprising veinlets and disseminated grains of ore minerals, commonly hosted by an igneous rock, known as a porphyry, in which relatively large crystals are set in a fine-grained groundmass. 10 www.MineralsUK.com deposits of PGE have been worked for centuries and were with sulphide-bearing chromitite in the lower sections of the principal source of platinum until the discovery of the ophiolites at Leka in Norway, Thetford in Canada, Al ‘Ays deposits in the Sudbury area of Canada and the Merensky in Saudi Arabia, Albania and New Caledonia. Although the Reef in South Africa. Significant platinum was extracted as concentrations of Pt and Pd in these ophiolites are locally a by-product from the alluvial gold working in western USA comparable with those in other magmatic settings, the size in the nineteenth century. Platinum was also previously of these occurrences is too small to support mining under worked by dredging river gravels beneath the Salmon current economic conditions. River, near Goodnews Bay, in western Alaska. This deposit produced an estimated 644 000 oz of platinum by 1975 Laterites (Barker et al. 1981). The operation closed in 1990. PGE Laterites are in situ residual deposits derived from were also formerly extracted from alluvial deposits in New prolonged tropical weathering which leads to the Zealand and British Columbia, Canada. Among the earliest breakdown of many rock-forming minerals, leaching of exploited platinum placer deposits, which are still worked certain elements and enrichment in others, chiefly iron and today, are those in the Choco District on the west coast aluminium. Under certain conditions and where the parent of Colombia. Russia still produces significant quantities of rock is ultramafic in composition, nickel may be enriched platinum from similar sources. Although recent data are to form an economic deposit. Exceptionally nickel laterites scarce, half of all Russian platinum production was derived may also contain elevated platinum concentrations, high from placer deposits in 1997 (Valtukh et al., 1999). enough to permit commercial extraction. Little data is available on PGE in nickel laterite deposits, but the most Ophiolites well known example of a platinum-bearing laterite deposit Ophiolite complexes are important sources of a number of is at Yubdo in Ethiopia. Platinum has been mined on a metals including copper and chromium. The basal mantle small scale at Yubdo since 1926 and current production is harzburgite and overlying ultramafic cumulate rocks within only about 100 oz per annum (Minerva Resources, 2009). ophiolites host important podiform chromite deposits in many countries, including Turkey, Russia, Albania and Veins and breccias Greece. Most early investigations suggested that the PGE Small quantities of PGE have been reported in association associated with podiform chromite were dominated by Os, Ir with base-metal vein deposits in some areas. The New and Ru. However, in the past 25 years significant enrichment Rambler deposit in Wyoming, USA, is a vein deposit of in Pt and Pd has been documented in association with copper sulphide minerals with high levels of palladium, deposits of this type in a number of ophiolite complexes. In platinum and gold. The deposit is interpreted to have the Unst ophiolite in Shetland, UK, high PGE concentrations, formed by hydrothermal fluids that leached palladium locally exceeding 100 ppm Pt+Pd, have been reported at and platinum from the surrounding mafic rocks before various stratigraphical levels (Gunn and Styles, 2002). The precipitating them at the intersection of a faulted mylonite highest values occur in the lower mantle harzburgite close and a major shear zone (McCallum et al., 1976). When to the basal emplacement thrust of the complex. High the mine closed in 1918 total platinum production was Pt and Pd values have also been reported in association estimated to have been 950 oz, with a further 16 870 oz of palladium (Hausel, 1997). Significant hydrothermal enrichment of platinum and palladium has also been reported in the copper-nickel sulphide occurrence at Rathbun Lake, Ontario, Canada. Here, average values of about 20 g/t Pd and 10 g/t Pt have been reported from copper-nickel ores hosted by sheared and altered gabbronorite (Rowell and Edgar, 1986). PGE have also been found in quartz veins with gold, silver and copper-nickel sulphides in north Westland, New Zealand (Challis, 1989).

The Waterberg deposit in Limpopo Province, South Africa, is a quartz-vein hosted platinum deposit that was mined between 1923 and 1926. The PGE mineralisation is hosted by post-tectonic quartz veins with fabrics similar to Disseminated chromite ore with very high PGE grades, epithermal46 style deposits. They are thought to have been Unst ophiolite, Shetland, UK. Scale bar 50 mm. produced by a hydrothermal event focused along a nearby Platinum

46Epithermal: relating to a mineral deposit formed within approximately 1 km of the earth’s surface and at temperatures between 50–200°C 11 www.MineralsUK.com major regional fault system. Grades up to 900 g/t Pt+Pd tonnes or more in size. Certain porphyry deposits may have been reported in the Waterberg lodes. contain economically important quantities of other elements such as molybdenum, gold, silver and, less Unconformity-related commonly, PGE. PGE-enrichment has been reported at Unconformity-related deposits host major resources of several localities including: Elatsite, Bulgaria; Skouries, uranium, mainly in Northern Territory, Australia, and in Greece; Santo Tomas II, Philippines; and Afton, Canada. Saskatchewan, Canada. Enrichment in gold and PGE The PGE contents of these deposits are generally low, less has been reported in some of these deposits. The most than 1 g/t, although locally values of a few g/t have been important example is the Coronation Hill deposit in the reported. PGE are recovered as a by-product from copper Pine Creek inlier of Northern Territory, Australia. PGE-gold refineries processing ore from porphyry deposits in the US and uranium-gold-PGE mineralisation occur at and below and Canada. Reserves in the Elatsite deposit have been a major unconformity that separates a deformed and estimated to be 185 million tonnes @ 0.38% Cu, 0.21 g/t metamorphosed basement complex from a cover sequence Au, 0.07 g/t Pd and 0.02 g/t Pt (Bogdanov et al., 2005). of haematitic quartz sandstone and sedimentary breccias. The mineralisation is thought to have been formed due to Shales and other sedimentary rocks interaction between low temperature oxidised brines from PGE enrichments occur in metal-rich black shales in the cover sequence and reducing rocks and fluids from the a number of geological settings, generally associated crystalline basement (Mernagh et al. 1994). Although a with continental rifting and sometimes accompanied by significant resource of gold, palladium and platinum was contemporaneous volcanic activity. PGE are not mined from defined in the 1970s, this has not been mined because these occurrences as, in most cases their contents are low, Coronation Hill was included in the Kakadu National Park up to a few hundred ppb, and the enrichment is restricted in 1994. The PGE occur in a range of Pt-Pd-Se-Sb minerals to thin beds, only a few cm thick. Examples are found unlike the mineral assemblages found in most other PGE in Early Cambrian shales in southern China with nickel- deposits. PGE enrichment, locally to very high grades, has molybdenum, in Devonian shales at the Nick property also been reported in the Jabiluka unconformity-related in the Yukon, Canada with attendant nickel-zinc, and in uranium deposit in Australia. Neoproterozoic49 shales in the Czech Republic associated with zinc and copper. The Serra Pelada gold-PGE deposit in the Carajás mineral province of north-east Brazil was discovered Much higher PGE values have been documented in the by local prospectors in the early 1980s. A major gold metalliferous deposits of the Permian Kupferschiefer rush ensued with more than 100 000 people working sedimentary rocks that underlie much of Germany, Poland the shallow sections of the deposit at its peak. Modern and Holland. The Kupferschiefer has long been exploited scientific studies of this deposit are few and consequently for its copper, silver, zinc and lead. More recently PGE its genesis is poorly understood in detail although an and gold enrichments have been found in shales over epigenetic47 origin, overprinted by supergene enrichment48, strike lengths in excess of 1.5 kilometres. Exceptionally is clearly evident. A recent estimate of the deposit size high precious metal values, up to 1900 g/t Au, 1900 g/t is 3.7 million tonnes @ 15.20 g/t Au, 4.09 g/t Pd, and Pd and 600 g/t Pt, have been reported in thin organic-rich 1.89 g/t Pt (Cabral et al., 2002). The largest part of the black shales (Kucha, 1982). PGE are also a significant resource is hosted by hydrothermally altered carbonaceous constituent of the major unworked gold deposit at Sukhoi and calcareous siltstones which unconformably overlie an Log in Russia. Here the precious metals are also hosted Archaean greenstone sequence. Other ores occur within by carbonaceous shales but later magmatic activity has iron-rich breccias and siliceous alteration zones. The been proposed to account for the observed mineralisation precious metal contents of the ores are commonly in the (Distler et al., 2004). g/t range, with bonanza grades up to 110 000 g/t Au and 16 000 g/t Pd+Pt locally reported. Carbonatites and alkaline complexes Phoscorite-carbonatite complexes are small, pipe-like bodies Porphyry deposits up to 3–4 km in diameter comprising complex multistage Porphyry deposits are large, low-grade copper orebodies deep-sourced intrusive igneous rocks of two principal types: of stockwork to disseminated mineralisation that typically carbonatite, an igneous rock composed of calcium and have grades of 0.4–1% Cu and can reach 1000 million magnesium carbonate phases, and phoscorite, an igneous

47 Epigenetic (in this context): a mineral deposit post-dating the age of the country rocks.

Platinum 48 Supergene enrichment: a mineral deposit produced by near-surface processes of leaching and transportation of metals followed by re-precipitation. 49 Neoproterozoic: the period of geological time from 1000 to 542 million years ago. 12 www.MineralsUK.com rock composed of three main mineral phases, magnetite, though attempts are being made to introduce more forsterite and apatite. These complexes are economically mechanisation into the workplace. Ore is blasted using important as sources of phosphate, iron, copper, uranium explosives then transported to the shaft using an and niobium in South Africa, Brazil and Russia. Parts underground rail system. Old workings are backfilled with of some of these complexes also contain significant waste material to improve ventilation by forcing air to enrichments in PGE: at Palabora in South Africa platinum travel through only those areas that are being worked, as and palladium are present in concentrations up to about 0.5 well as providing more roof support. Underground mining g/t and are recovered as a by-product of copper production. is also employed in the Noril’sk-Talnakh, Sudbury and Osmium and iridium are present in greater abundance (few Stillwater deposits. g/t) at Palabora. Values up to ca. 3 g/t Pt and 1 g/t Pd have also been reported in the Catalão and Ipanema complexes in Opencast and underground mining are sometimes Brazil. A wide range of PGM has been reported in sulphide combined at a single mine, and may take place concentrates from the phoscorite-carbonatite at Kovdor in simultaneously in order to access shallow and deeper the Kola Peninsula, Russia. However, the PGE abundance in parts of an ore body. The open-pit mine may be in these ores is not well known. operation while the underground workings are being developed. Recently there has been a sharp rise in the PGE mineralisation also occurs in some composite alkaline number of combined surface and underground operations intrusive igneous complexes. The most well known in South Africa working the lower-grade, but larger example is the Coldwell Complex in north-western Ontario resource, of the UG2 reef. Other examples include the where several prospects are under evaluation. The most Amandelbult and Marikana mines in South Africa, and the advanced is the Marathon deposit where a resource of Lac des Iles mine in Canada. 79 million tonnes @ 0.76 g/t Pd, 0.23 g/t Pt and 0.27% Cu has been defined (Marathon PGM Corporation, 2008). Extraction methods and processing Extraction methods The method used to mine platinum-bearing deposits is dependent on their size, grade and morphology. The high price commanded by platinum and its high concentration in units such as the Merensky Reef allow it to be mined using either open-pit methods or underground methods, or a combination of both.

Underground mining Underground extraction uses a variety of standard mining methods depending on the characteristics of the orebody. The deepest currently operating platinum mine is at Northam in South Africa where mining takes place at a maximum depth of 2.2 km. Due to the high temperatures at this depth, Northam employs ‘hydropower’ technology which uses water, cooled on surface to 5ºC, to power its drilling machines and cool working places. Hydropower is also employed by other companies including Lonmin Northam Platinum Mine, South Africa. © Northam Platinum Plc and Anglo Platinum Ltd. Other underground operations in the Bushveld Complex include the Anglo Open-pit mining Platinum’s Rustenburg and Union Mines, and Impala’s Surface mines are generally cheaper and safer to operate Crocodile River Mine. Typically, these operations use than underground mines. Open-pit mining is most labour-intensive drilling and blasting techniques, appropriate for near-surface (<100 m), lower-grade, steeply Platinum 50 Overburden: waste material that lies above a mineral deposit. 51 Gangue: the undesirable or unwanted minerals in an ore deposit. 13 www.MineralsUK.com dipping or massive ore bodies where large-scale surface Following milling, additional water is added to the excavations would not cause significant environmental powdered ore to produce a suspension and air is blown impact. This method typically involves removing the upwards through the tanks. Chemicals are added to the overburden50, digging the ore or blasting with explosives, mix, making some minerals water-repellent and causing then removing the ore by truck or conveyor belt for air bubbles to stick to their surfaces. Consequently, these stockpiling prior to further processing. minerals collect in froth at the surface and are removed as a metal concentrate. This process is known as froth flotation. Examples of surface mining operations for PGE include the Mogalakwena (formerly PPRust) operation in South Africa, The greatest losses of PGM occur during crushing, milling and the Yubdo laterite deposit in Ethiopia. and flotation, mainly due to the highly variable mineralogy and mode of occurrence of PGM, which may be associated Processing with base-metal sulphides, silicate minerals or chromite. After mining the ores are processed to increase their For this reason metallurgical operations normally treat UG2 platinum content. Concentration is normally carried and Merensky ore separately to maximise PGM recovery. out at, or close to, the mine site and involves crushing Many operations employ two stages of milling and floating the ore and separating platinum-bearing and gangue51 conducted in series, known as mill-float-mill-float or MF2 minerals, using a range of physical and chemical operations, in order to maximise PGM recovery. processes. Subsequent smelting and refining may be carried out at or near the mine, or concentrate may be Following flotation, the final concentrate is dried to less transported or exported for processing to metal. Different than 0.5 per cent moisture before smelting. procedures are used for processing sulphide-poor ores (e.g. Merensky and UG2) and sulphide-dominant ores Smelting (e.g. Noril’sk) due to their chemical, mineralogical and The purpose of smelting is to recover as much metal as physical differences. possible from the concentrate. The matte-smelting process produces a silicate melt (slag) from which an immiscible PGE-dominant ore sulphide melt (matte) separates due to density differences. Comminution52 and concentration Matte smelting takes places in furnaces at temperatures Ores from the Merensky Reef and UG2 reef are generally exceeding 1300ºC. Fluxes such as limestone are added sulphide-poor with platinum and other PGE present in to the smelter to reduce the melting temperature of the a large variety of discrete PGM. The initial phase of processing both reef type ores is identical. Ore is fed into a primary crusher from where it undergoes one or more stages of secondary crushing. At each stage vibrating screens allow material of the appropriate size to pass on to the next part of the processing circuit. Crushing, followed by fine grinding, also known as milling, is used to maximise separation of the ore minerals from the gangue. The crushed ore is mixed with water to create a slurry which is fed into a series of grinders until a powder of the required grain size is produced.

Some mines have introduced one or more additional stages after crushing and milling to optimise PGE recovery. These include magnetic separation and dense media separation. Where the PGE are known to be present within the crystal structure of pyrrhotite, then pyrrhotite may be magnetically separated, collected and treated separately. Dense media separation is used to remove lighter silicate minerals from the denser chromite and PGM after initial crushing and prior to milling. This significantly reduces the volume of ore to be milled and subsequently floated without reducing PGM recoveries. Smelter complex, Western Platinum Mine. © Lonmin. Platinum

52 Comminution: the process of crushing and grinding a rock into powder. 14 www.MineralsUK.com

Figure 3 Schematic flowsheet for typical processing of PGE-dominant ores.

platinum and base-metal sulphides which accumulate in is treated differently and the matte is slow cooled to the matte, known at this stage as green matte. promote the production of a copper-nickel alloy containing the PGE. The resulting matte is then crushed and the UG2 ore, which is low in sulphur and high in chromite, sulphide component separated magnetically. It is then sent requires special treatment. Its high chromium content directly to the precious metal refinery. can cause significant operational problems and lead to higher losses of PGM within the slag. UG2 ore is not Refining smelted on its own because an immiscible matte will not Refining to produce high-purity platinum products is form. It is usually blended with Merensky concentrate, or a very lengthy and complicated process. The methods rarely with other sulphur-rich ores, to produce the matte. involved differ from company to company and for The percentage of chromite in the smelted ore must be commercial reasons the techniques used are closely carefully managed to prevent PGE losses. guarded secrets. However, in general, the process consists of a series of hydrometallurgical operations. Once the matte has been tapped from the smelting Initially, the white matte is transferred to the base metal process, the liquid metal undergoes a process known as refinery for base metal removal. The PGE-bearing residue converting. This involves blowing air, or oxygen, into the from the base metal refinery, containing over 60 per cent matte over a period of several hours to oxidise contained PGE, is transferred to the precious metal refinery for iron and sulphur. Silica is added to the matte to react with separation and purification of the PGE. the oxidised iron to form a slag that can be easily removed, while the sulphur is collected to produce sulphuric acid. All commonly used refining processes separate and produce The converter matte, known as white matte, consists of individual PGE by utilising differences in their chemistry. copper and nickel sulphide with smaller quantities of iron Refining is achieved either through a series of dissolution and sulphides, cobalt and PGE. This is usually cast into ingots precipitation stages involving PGE salts, or by using a technique and is then sent to the base metal treatment plant for known as total leaching, which is followed by sequential metal recovery of the base metals. However, matte treated by separation with the aid of solvent extraction. This process is Anglo Platinum, the largest platinum producer in the world, shown in Figure 3. Platinum

15 www.MineralsUK.com Nickel-copper-dominant ore PGE-bearing nickel-copper-dominant ores, such as those from Noril’sk and Sudbury, are treated somewhat differently to PGE-dominant ores due to their higher sulphide content and different mineralogy. Several types of ore are recognised depending on their sulphide concentration and textures, including massive ores with in excess of 70 volume per cent sulphides. PGE occur in a wide variety of PGM in these ores.

At Noril’sk, the ore is crushed and milled before undergoing gravity concentration in a centrifugal-type concentrator to recover up to 40 per cent of the PGE. Froth flotation is then used to produce a metal concentrate prior to treatment at the smelter. This process involves mixing the finely ground ore with water and special chemicals to make the valuable minerals hydrophobic. The mixture is then agitated and air blown through to produce bubbles to which the ore minerals attach themselves and which rise to the surface where they are skimmed off. This metal concentrate, once dried, is sent to the smelter where it is roasted, smelted and converted to produce a copper-nickel- PGE matte, together with slag as a waste product. The matte is granulated, wet-ground and then treated in the Platinum smelting. © Lonmin. base metal refinery where pressure oxidation leaching is used to produce concentrates of nickel, copper and cobalt. anode slimes are then added to other slimes produced The copper concentrate, containing 70% to 71% copper, from the production of nickel, together with the gravity 0.2% to 0.6% iron, 0.4% to 0.7% nickel, 26% to 28% concentrate produced after the initial crushing and milling. sulphur and almost all the PGE and gold, is then smelted This mixture is smelted again to produce a PGE-bearing in furnaces to produce copper blister (98.5% to 99.5% matte. The matte is then pressure-leached to produce copper) with PGE and gold. The copper is then further a silver concentrate (AgCl), and two PGE concentrates refined using electrowinning to produce pure cathode containing platinum and palladium and the other PGE. This copper with the PGE remaining in the anode slimes. The process is shown in Figure 4.

CONCENTRATOR SMELTER SO2 (to sulphuric acid)

Crushing Froth Thickening, Roasting, & flotation Filtering, Smelting, Wet grinding Dewatering, Converting grinding Drying

Bulk Cu-Ni Slag Ground ore concentrate Matte Ground PGE - b ea ri ng m a Impurities t Furnace te

to PRECIOUS METAL SMELTER ELECTROLYTIC SMELTER Cu metal BASE METAL REFINERY REFINERY to REFINERY Ni metal

Selective Electrolysis CuSO4 solvent extraction NiCO3 Cu + Ni removal Pt+Pd

PGE - bearing PGE - bearing Rh+Ru matte anode slimes Cu blister + PGE Cu concentrate + PGE H2SO4 Au, Ag + other PGE Pressure Furnace Anode slimes Furnace oxidisation leaching

HYDROMETALLURGICAL PYROMETALLURGICAL HYDROMETALLURGICAL PYROMETALLURGICAL HYDROMETALLURGICAL PROCESSES PROCESSES PROCESSES PROCESSES PROCESSES Platinum Figure 4 Schematic flowsheetfor typical processing of nickel-copper-dominant ores. 16 www.MineralsUK.com

Froth flotation plant at Noril’sk. © Johnson Matthey Plc.

Other PGE sources these slimes. The processing varies from plant to plant In many operations the PGE are extracted as a by-product but generally involves leaching, smelting and refining. The of nickel, copper and cobalt production. The metallurgical quantities of platinum produced by these copper refineries, process is therefore designed around the main product, although relatively small, are highly significant in economic normally nickel, whilst maximising PGE recoveries. terms. For example, 3.85 tonnes of palladium-platinum concentrate was produced by Noranda (now Xstrata) in Several methods are used to extract PGE from base metal 1988, and 2 tonnes of palladium-platinum sponge was ores. However, they all treat the matte produced at the produced in 1983 from the copper refinery at Pori, Finland, smelting stage. At Vale’s Sudbury operations, the matte is formerly owned by Outokumpu (now Boliden). treated by flotation and magnetic separation to produce separate nickel, copper and precious metal concentrates. The precious metal concentrates are treated in a two- Specifications and uses stage pressure leaching process to dissolve first the nickel PGE are sold in a number of forms including pure metal and cobalt, and then the copper, selenium and tellurium. and a variety of compounds, solutions and fabricated This concentrate, containing 60% to 80% PGE + gold, products. These are produced by a small number of together with small quantities of silver and base metals, is specialist companies such as Johnson Matthey and BASF. then refined to produce high-purity individual elements. The catalytic properties of the PGE, which are the basis Another method, used by Xstrata’s Sudbury operations, of most of their important applications, are exploited in recovers base metals and PGE by treating the nickel- two main sectors: emission control systems and process copper-cobalt matte with chlorine. The nickel and catalysts for industrial applications. Other important cobalt are recovered as pure metals whilst the copper properties of the PGE that make them useful for many is contained in a sulphate solution. After removal of the additional purposes include their strength, high melting copper the PGE remain in the residue. This is smelted to point, and resistance to corrosion. The major applications matte in an electric furnace before being granulated and of platinum and palladium are shown in Figures 5 and 6. leached with hydrochloric acid and chlorine to obtain the individual PGE metals. Autocatalysts The largest use of platinum, palladium and rhodium The copper concentrates derived from many copper ores is in autocatalysts, which are used to convert noxious contain small quantities of PGE. In processing these ores emissions (carbon monoxide, oxides of nitrogen and the PGE will be present, together with gold and silver, in hydrocarbons) from car exhaust systems to harmless non- the anode slimes. Most large copper refineries therefore toxic products. Demand for PGE in autocatalysts has grown normally operate a precious metals recovery plant to treat markedly from the 1970s onwards as various countries Platinum

17 www.MineralsUK.com 18 Platinum Figure 6 Applications of palladium, 2008 (Johnson Matthey). platinum isthe materialofchoiceinAsiawhere the its longstanding priceadvantageoverplatinum. However, used ingasoline-poweredvehicles chieflyonaccountof Currently palladiumisthemajor constituentofcatalysts in responsetotechnologicalchanges andpricevariations. used inautocatalystshavevaried considerablyovertime The quantitiesandproportionsofplatinumpalladium vehicles. legislation settingstandardsforemissionsfrommotor followed theleadofUSAandJapanintroduced Figure 5 Applications of platinum, 2008 (Johnson Matthey). % 16 19 6% % Ot El Au Gl Au Pe ec he to 5% as tr to 11 tr 8% ca r ol ca on s % eu ta 3% ta 3% ic ly m ly s 4% st st 5% 5% 7% Je Ch Ot Ch In 1% we ve em he em st lle r ic ic me al ry al nt In De El Je ve nt ec we st al tr me lle 52 ic % 55 nt al ry % predominant. to itspriceadvantageoverplatinum,butthelatterisstill amount ofpalladiumusedinthedieselsectorresponse trucks. Therehasalsobeenasignificantincreaseinthe demand forplatinuminmedium-andheavy-dutydiesel America andJapanhavealsoledtosignificantlyincreased engine. MorestringentemissioncontrolsinEurope,North where morethan50percentofallnewcarshaveadiesel this isthemaincontributiontoplatinumdemandinEurope and filtersfittedtodiesel-poweredvehicles.Consequently Platinum isalsothechiefactivecomponentincatalysts preferred onaccountofitshighersulphurtolerance. quality ofgasolinesuppliesisvariableandplatinum palladium after autocatalystsandelectronics applications. for platinumit remains thethirdmostimportant useof demand forpalladiuminjewellery issignificantlylessthan price advantagesoverplatinum andgold.Although palladium jewelleryitself,where itenjoysconsiderable either asacomponentofwhite goldand,increasingly, as 1.37 million ozin2008.Palladiumisalsousedjewellery, in thelastdecadefrom2.88millionoz1999to demand forplatinuminjewelleryhasfallenconsiderably increasingly popularinEuropeandChina,althoughoverall especially inJapan.Inrecentyearsithasbecome Platinum haslongbeenwidelyusedinjewellery, Jewellery of specialistglassesandthechemicalssector. areas whererhodiumisimportantincludethemanufacture which accountformorethan80percentofitsuse.Other palladium, rhodiumisacriticalcomponentofautocatalysts gross) isonlyabout5percentofthatforplatinumand Although globaldemandforrhodiumin2008(689 000oz © JohnsonMattheyPlc. Simplified cut-awaythroughanautocatalyst. www.MineralsUK.com

19 Platinum capacity. ©JohnsonMatthey. Platinum isusedinharddisks toincreasetheirstorage materials andtopeelawaycleanlywithouttearing. the surfaceonwhichtheyarecoatedtostickother sensitive adhesives(PSA)whicharedesignedtoallow other sectors.Well knownexamples includepressure- used intheaerospace,automotive,constructionandmany consistency rubbersandliquidsiliconewhichare speciality siliconesforwaterrepellentcoatings,high important inprocesscatalystsforthefabricationof conversion ofammoniatonitricacid.Platinumisalso explosives whereplatinumisusedasacatalystinthe most importantareinthemanufactureoffertilisersand Platinum hasmanyusesinthechemicalsindustry. The Chemicals Platinum jewellery. ©JohnsonMattheyPlc. Platinum and platinum alloys are used in the fabrication fabrication the in used are alloys platinum and Platinum Glass plating ofconnectorsinsidecomputers. circuits (HIC),usedmainlyintheautomotivesector, andin while otherimportantapplicationsareinhybridintegrated palladium is used in multi-layer ceramic capacitors (MLCC), over rivalssuchasgold.Alargeproportionofthis of palladiumwhereitenjoysasignificantcostadvantage The electronicsindustryisthesecondlargestconsumer purchasing byharddiskmanufacturers. per centto225 000oz,largelyasaresultofreduced demand fromtheglobalelectricalsectorfellby11.8 has risenconsiderablyinrecentyears.However, in2008 Accordingly thedemandforplatinumthispurpose disk drives,especiallyforvideoandaudioapplications. requirement toincreasethestoragecapacityofhard electronic devicesofalltypeshasincreasedsothe coating oncomputerharddisks.Asthemarketfor Platinum isanimportantcomponentofthemagnetic Electrical andelectronics Canadian Maple Leaf. including theAmericanEagle, theAustralianKoalaand long periods.Various platinumcoinshavebeenissued be boughtandkeptasarepository ofvalue,oftenfor been introducedtomeetdemand forplatinumwhichcan last thirtyyearsanumberofbars, ingotsandcoinshave internationally standardizedformandpurity. Duringthe is acceptedasameansofexchangebyvirtueits Like goldandsilver, platinumisatangibleassetwhich Investment worldwide forproductsderivedfrompetroleum. very difficulttomeetthedemandsofgrowingeconomies pellets orbeads.Withoutthesecatalystsitwouldbe platinum ontoanaluminasubstrateintheformofsmall fibres. Theseprocessesusecatalystsmadebycoating manufacture ofplastics,syntheticrubberandpolyester production ofpetrochemicalfeedstocksusedinthe Platinum iscriticaltotherefiningofpetroleumand Petroleum refining glass. fibre and screens panel flat are which of important most the products, glass of range large a of manufacture the in used is equipment Platinum-based equipment. the of life longer and performance improved to contributing alloys these of component important an is Rhodium temperatures. high at it with react not do and glass molten of action abrasive the withstand to able are materials These glass. molten form and channel hold, that vessels of www.MineralsUK.com 20 Platinum 400 000 oz,respectively. for platinumandpalladiumin2008were425 000oz platinum bars,especiallyin2008.Netinvestmentdemand funds (ETFs)launchedin2007andincreasedsalesoflarge platinum andpalladiumthroughtwoexchange-traded situation changedagainwithincreasedinvestmentinboth two percentofglobaldemand.In2007and2008the fell away, withsalesin2005accountingforonly about coins. However, inthelastdecadeinvestmentdemand demand tobeaccountedforbysalesofplatinumbarsand from SouthAfricaledtoasignificantproportionofglobal In the1980sconcernoversecurityofplatinumsupply catalytic automotive andbiomedicalsectors. applications. Themostimportant oftheseareinthenon- Platinum isalsousedinminor amountsinahostofother Others largest consumer of palladium in dental applications. are used in Germany and North America, while Japan is the cost considerations. Most platinum-containing dental alloys the use of palladium has increased chiefly in response to dentists for many decades. However, from the 1980s onwards Platinum-containing high gold alloys have been used by iridium aresometimesadded. dentists andtheirpatients.Smallamountsofrutheniumor technical performance,priceandthepreferencesof choice ofalloydependsonmanyfactorsincludingthe usually mixedwithgoldorsilverinvaryingratios.The bridges andcrowns.Thepalladiumplatinumare important componentsofdentalalloysusedininlays, Palladium and,toamuchlesserextent,platinumare Dentistry purposes. ©Lonmin. Platinum ingotsareusedastoreofwealthforinvestment The abilityofplatinum,incertainchemicalforms,toinhibit Biomedical worldwide. increased is regulation environmental as grow will application this in platinum for demand future the In emissions. monitor to used is sensor second a USA, the as such countries some in and, burned is mixture air-fuel correct the that ensure to converter catalytic gas exhaust an with equipped cars all to fitted are sensors These cars. modern of systems management engine the in sensors oxygen of constituent important an also is Platinum steadily. increasingly is Japan and Europe in use their and plugs platinum with fitted are America North in vehicles new All pollution. reduced and combustion efficient more costs, service lower to contributes therefore It electrodes. metal base traditional than performance better and life longer much a has it where engines gasoline in plugs spark of electrodes the in is platinum of use growing A Non-catalytic automotive fountain pennibs. screens. Smallamountsarealso usedinjewelleryand industries, andtheproduction offlatplasmadisplay Other applicationsincludethe electronicsandchemical technology whichisusedinhard diskdrivemanufacture. area forrutheniumisinperpendicular magneticrecording broadly comparablewiththatofrhodium.Themaingrowth Global demandforruthenium(669 000ozin2008)is Uses ofruthenium,iridiumandosmium disease. into thearteriesfornon-invasivetreatmentofheart important componentsofcatheterswhichareintroduced heartbeat. Platinummarkerbandsandguidewiresarealso defibrillators (ICD)usedinthetreatmentofirregular in heartpacemakersandimplantablecardioverter implanted inthebody. Platinumelectrodesareused component ofvariousbiomedicaldevicesthatare small complexcomponents,platinumisalsoanimportant conductivity anditsabilitytobefabricatedintovery On accountofitschemicalinertness,highelectrical cisplatin. various cancersandarebothnowmorewidelyusedthan cisplatin, havesincebeenintroducedforthetreatmentof carboplatin andoxaliplatin,whicharelesstoxicthan bladder andlungcancers.Two otherplatinum-baseddrugs, and iswidelyusedinthetreatmentoftesticular, ovarian, drugs. Thefirstofthese,cisplatin,wasintroducedin1977 cell divisionisthebasisofitsuseinarangeanti-cancer www.MineralsUK.com 21 Platinum on customertrials aroundtheworld.©Mercedes-Benz. The MercedesF-CellAclassis afuelcellvehiclecurrently the adoptionofincreasinglystringentenvironmental developed formoderndieselenginesinlinewith Sophisticated emissioncontrolsystemsarebeing expanding markets New technologiesand filaments inlightbulbsandmedicalimplants. iridium, whichisusedinpentips,electricalcontacts, is usedinsmallamountsanalloywithplatinumand in thechemicalindustryandsparkplugtips.Osmium (102 000 ozin2008).Itisusedchieflyprocesscatalysts Annual demandforiridiumisconsiderablysmaller transport becomes an imperative. A fuel cell is an an is cell fuel A imperative. an becomes transport non-polluting and efficient fuel for demand the as sector cell fuel the in anticipated is palladium, also possibly and platinum, for demand of growth Considerable manufacture. industrial processessuchascement,glassandnitricacid include generatorsandturbinesaswellmany with significantgrowthpotential.Theseapplications controls fromstationaryapplicationsisanotherarea The useofplatinum-groupmetalcatalystsinemission Phillips, 2009). single systemknownasa‘four-way catalyst’ (Twigg and that gasandparticulateemissionswillbecontrolledbya particles fromexhaustemissions.Inthefutureitislikely have beendevelopedforcarsinordertoremovesoot systems employingplatinumorplatinum-palladiumfilters addition tothecontrolofgaseousemissions,various measures willbeadoptedelsewhereinthefuture.In India from2010onwardsanditisverylikelythatsimilar are duetobeintroducedinRussia,China,Braziland legislation inNorthAmericaandtheEU.Similarstandards been developed in recent years but the first commercially commercially first the but years recent in developed been have vehicles demonstration cell-powered fuel Various remain relativelyexpensive. current manufacturingcapacityissmallandtheunits cell technologybeganinearnest2007althoughthe portable electricalequipment.Commercialisationoffuel date focussedondevicesforpoweringcars,housesand to developfuelcelltechnology, withmostattention to A hugeamountofpublicandprivateresearchisunderway efficiency. fuel greater potentially their also but operation, clean their notably most generation, power for used technologies other over advantages major offer cells Fuel supplied. are fuel and oxygen while electricity produce to continue but power of out run not do they batteries, unlike that, so externally supplied are air) or (oxygen oxidant and hydrogen, normally fuel, The devices. these of component key a is metals platinum-group comprising catalyst A by-product. a as heat with electricity into directly reaction chemical a of energy the converts that device electrochemical demand forruthenium forthispurpose. elements. Asthemarketforair travelexpandssowillthe which maycomprise3to6 weightpercentofthesetwo strength, durabilityandresistance tocreepofthesealloys, The rutheniumandrheniumare usedtoimprovethe nickel-based superalloysinturbine bladesforjetengines. together withrhenium,isincreasinglybeingusedin alloys isanotherareaofexpectedgrowth.Ruthenium, The useofplatinum-groupmetalsinarangespecialist and batteries. military applicationswheretheycouldreplacegenerators of supply. Anotherpotentiallylargeuseoffuelcellsisin businesses, bothasaprimarysourceandbackup supply instationaryapplicationssuchashousesand where thepotentialishuge,tocombinedheatandpower electronics, suchaslaptopcomputersandmobilephones, utilisation offuelcells.Theseincludeconsumer There aremanyotheropportunitiesforthefuture fleet. vehicle cell fuel its of evaluation the in aid to Birmingham of University the at 2008 in opened station fuel hydrogen UK’s The first hydrogen. of tank single a on miles 200 exceeding range a have and minutes in refuelled be can cars cell fuel contrast In recharge. to hours several takes and range limited only offers currently technology Battery cars. powered gasoline- to alternatives practical truly be to now appear vehicles These 2008. in California in launched was Clarity, FCX Honda car, the cell fuel available www.MineralsUK.com 22 Platinum and easierthaninthepast. (ETFs) makes investment in platinum and palladium simpler medium-term. Theavailabilityofexchange-tradedfunds investment sectorin2008maycontinuetheshort-and the increaseddemandforplatinumandpalladiumfrom Consequently, giventhecurrentglobaleconomic turmoil, for storingwealthintimesofeconomicuncertainty. Like gold,platinumisviewedbymanyasasafehaven heart diseasesisalsoexpected. prostate cancer. IncreaseduseofICDsforthetreatment being developed,suchassatraplatinforthetreatmentof expected tocontinuegrow. Newanti-cancer drugsare The useofplatinuminbiomedicalapplicationsisalso tonne. Measured and indicated mineral resources contribute million oz of platinum at a combined grade of 7.54 grams per area are reported as 63 million oz of palladium and 16 Proven and probable ore reserves in the Noril’sk-Talnakh the USA, and the Penikat and Keivitsa Complexes in Finland. Skaergaard Complex in Greenland, the Duluth Complex in previously thought to be uneconomic. These include the has led to renewed interest in several areas and deposits general rise in the price of platinum over the last 20 years in the Noril’sk-Talnakh district of Russia. In addition, the deposits, for example in the Sudbury area of Canada and the Stillwater Complex in the USA, and in nickel-copper parts of the world, notably in the Great Dyke in Zimbabwe, Africa, there are also considerable resources in other Whilst the majority of PGE resources are located in South if market conditions were favourable. Bushveld Complex that could potentially be exploited for PGE greater depth. In addition, there are several other units in the significant potential to exploit further platinum resources at already taking place at Northam, and there is therefore two kilometres. Platinum mining below two kilometres is Merensky, UG2 and Platreef down to a depth of approximately However, these estimates are based only on resources in the for at least 40 years based on current production rates. 1999). This alone would be sufficient to meet global needs 75 per cent of the world’s total platinum resources (Cawthorn,204 million oz, with potential resources of 937 million oz, or proven and probable reserves of platinum are in the order of Complex due to its enormous size. One study estimated that estimate for the total quantity of platinum in the Bushveld world platinum resources. It is difficult to give a reliable The Merensky, UG2 and Platreef in South Africa dominate Resources World resources and production Zimbabwe, Canada(LacdesIlesmineandSudbury),in USA. Smallquantitiesofplatinumareproducedin Noril’sk operations,andtheStillwaterMineinMontana, Other majorsuppliersofplatinumincludeRussia,fromthe for almost78percentofworldproduction(Figure7). South Africaisthelargestplatinumproducer, accounting geological problemsandlabourdisputes. unscheduled maintenanceshutdowns,safetyconcerns, to lowerproductionfromSouthAfricanminescausedby declined forthesecondconsecutiveyear, principallydue (Johnson Matthey, 2009).World platinumproduction supply andcausedadeficitof375 000ozin2008 6.35 million ozin2008,althoughdemandstillexceeded Global demandforplatinumfellby5 percentto Production the Stillwater Complex in Montana, USA (Norilsk, 2006). platinum in the proven and probable reserve categories in Company has a reported 23 million oz of palladium and million oz of platinum (Norilsk, 2006). The Stillwater Mining an additional almost 140 million oz of palladium and over 40 Statistics database. (kilograms). Source: British Geological Survey World Mineral Figure 7 World mine production of platinum 2007 recent productionfiguresareunknown. produced fromtheJinchuanComplexinChina,although Australia, as a by-product of nickel mining. 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2002 0 brought about by the global economic recession. in 2008 in response to reduced demand and lower prices in platinum production and this trend is expected to continue and a shortfall in stocks. In 2007 there was a slight decrease steadily in response to increased demand in autocatalysts In the decade up to 2006 production of platinum rose slight fallinproductionfromNoril’sk andStillwater. slightly in2007comparedwith2006figurescausedbya Africa (Figure8).World palladiumproductiondipped Production ofpalladiumisdominatedbyRussiaandSouth end ofOctober2008. Iles operation,thoughthisminetemporarilyclosedatthe whilst CanadaproducedmarginallymorefromtheLacdes Australia producedslightlylessPGEin2007than2006, dormant Crocodile River mine (Impala) on the Western Limb. Twickenham and Lebowa mines), as well as the previously Limb of the Bushveld Complex (e.g. Anglo Platinum’s on stream. The new mines include several on the Eastern substituting palladium for platinum due to the significant production since 2002 is due to vehicle manufacturers again palladium by platinum in autocatalysts. The rise in palladium a result of the high price level, leading to substitution of past decade (Figure 9). There was a sharp fall in 2002 as Overall the production of palladium has declined in the 2003 2004 Mi Mi 2005 ne ne produ produ 2006 ct ct io io www.MineralsUK.com n n 2007 of of Pd Pt

24 Platinum the UKandNorway. many nickel-coppermattesfromCanadaareprocessedin those inwhichtheyhavebeenproduced.Forexample, quantities ofmattesareprocessedincountriesotherthan wire, mesh).Platinumtradeiscomplexassignificant manufactured orsemi-manufacturedforms(e.g.ingots, unwrought (ores,concentrates,powders)orin Platinum istradedinmanyforms,generallyeither World trade reduced palladium demand in 2008 and 2009. that the global economic recession will lead to significantly price differential between the two metals. It is anticipated and exportcharts duetouncertaintiesregarding thereliabilityof data.Nationswith *indicate2007figures. Commodity Trade StatisticsDatabase(UNComtrade). Trade figuresforIndonesia havebeenexcluded from theimport Figure 10Majorimportersof platinum metal,concentratesandintermediate products,2008.Source:UnitedNations (>67 nations. These include the UK, (>90 Imports of platinum are dominated by leading industrialised 100 000 Platinum (kilograms) 000 kg), Switzerland (>67 10 00 20 00 30 00 40 00 50 00 60 00 70 00 80 00 90 00 0 0 0 0 0 0 0 0 0 0

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www.MineralsUK.com Ital y Re p. of Ko rea* 25 Platinum US$250 the price hovered around US$400 over the last decade (Figure 12). Throughout the 1990s, The price of platinum has experienced periods of volatility have amarginaleffectonthe platinumprice. relationships, althoughmovementsinthegoldpricedo predominantly determinedbynormalsupplyanddemand metal inindustry. Consequentlythepriceofplatinumis Unlike gold,platinumisanimportantandwidelyused cash and immediate delivery in plate or ingot form. prices. In the spot market platinum and palladium are sold for base price and the London Platinum and Palladium Market market price, the Engelhard base price, the Johnson Matthey These include the LME settlement price, the European free (minimum 99.9 per cent) metals in US dollars per troy oz. A number of daily market prices are quoted for the pure Prices and exportchartsduetouncertaintiesregardingthereliabilityof data.Nationswith*indicate2007figures. Commodity Trade StatisticsDatabase(UNComtrade).Trade figuresforIndonesiahavebeenexcludedfromtheimport Figure 11Majorexportersofplatinummetal,concentratesandintermediate products,2008.Source:UnitedNations Platinum (kilograms) 100 000 120 000 140 000 160 000 20 000 40 000 60 000 80 000

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Ge rm any manufacturers in catalyticconverters.However, since the time.Thiswasdueto highlevelofusebyvehicle early 2001andwasalmostdouble thepriceofplatinumat The priceofpalladiumpeaked atoverUS$1000perozin just over US$1200 by the end of June. Journal, 2008). The price began to rise again in 2009 reaching platinum to just over US$800 the middle of the year, caused a dramatic fall in the price ofin supply. However, the global financial crisis, which begandemand, in principally by vehicle manufacturers, and a shortage (Metal Bulletin, 2009) attributed to a combination of rising and reached a record level of US$2276 The price continued to rise through the first quarter of 2008 oz in August 2001, to just over US$1500 dramatic increase in the price of platinum from US$420 in catalytic converters increased markedly. This led to a the twentieth century, demand for platinum and palladium produce less pollution was introduced towards the end of the early 1980s. However, after legislation requiring cars to Japa n*

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per 26 Platinum conductive elements ofhybridintegratedcircuits (HIC)was made withnickel. Theuseofpalladiumpastes forthe one stagemorethanhalfofthe MLCCsproducedwere 2000s sawmanufacturersswitch tousingnickel,andat phones. Therapidriseinpalladium’s priceinthe early capacitors (MLCCs),whichare widelyusedinmobile the electronicsindustrytoproducemulti-layerceramic In thelate1990s,85percentofpalladiumwasusedin certain applications. alternative cheapermaterialstosubstituteforthePGEin catalysts. Considerableresearchisalsodevotedtofinding reduction inthequantitiesofPGEusedautomotive advances inrecentyearshaveallowedaconsiderable reduction inperformance.Forexample,technological material inaparticularapplicationwithlittleorno in recyclingandthriftingofthePGEi.e.usingless Recent highpriceshaveensuredagrowinginterest substitution Recycling, thriftingand June 2009thepricehadralliedtoUS$250peroz. downturn reduceddemandforthemetal.Atendof US$200 perozbytheendofyearaseconomic US$500 perozin2008,buthadfallenbacktojustunder US$200 andUS$400peroz.Thepricebrieflysurpassed 2001, thepriceofpalladiumhasfallenbacktobetween Figure 12.Platinumandpalladiumprice(JohnsonMattheybase (unfab)$pertroyoz(MetalBulletin).

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autocatalysts. Scrap autocatalystsaremelted atavery consumer scrap, suchaselectronicitems,jewellery, and is nouniversaltechniqueforrecovering PGEfrompost- 1.1 million ozPdin2008(Johnson Matthey, 2009).There oz Pdrecoveredin1999tojust over1 millionozPtand quantities haverisenfrom420 000 ozPtand195 are particularlyimportantsourcesforrecycledPGE,and considerable recyclinginmanyapplications.Autocatalysts The highpricescommandedbyPGEhaveledto will continuetogrowstrongly. medium andlongtermdemandforPGEinthesesectors especially ontheautomotiveindustry, itislikelythatinthe economic recessionhashadasignificantimpact, in demandforPGErecentyears.Althoughtheglobal and glassindustries,therehasbeenverystronggrowth In certainsectors,suchastheautomotive,electronics catalytic metal. diesel catalystswhichformerlyusedplatinumasthesole to increasetheproportionofpalladiumplatinumin catalysts forpetrolcarswithmanufacturersmoving there hasbeenincreaseduseofpalladiuminthree-way due tofluctuationsinprices.Forexample,recentyears some PGEhavebeensubstitutedforothers,particularly In additiontothesubstitutionofPGEforothermetals, silver-palladium pasteswithhighersilvercontents. 2000s anddemanddeclinedasmanufacturersmovedto also affectedbythehigherpriceofmetalinearly July 2004

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Jan 2009 Pd Pt 27 Platinum addition, grainsofplatinum-groupmineralsandother origin hasbeendocumented(GunnandStyles,2002).In mineralisation of magmatic, hydrothermal and near-surface current economicinterest.However, in-situPGE-bearing There arenodepositsofPGEinBritainthat Occurrences andpotential Focus onBritain precious metalsrefinery. or iron,andtheresultingPGEconcentrateisrefinedata from thisprocessisthenleachedtodissolvethecopper catalyst substrateanddissolvethePGE.Thealloyobtained high temperaturewithironorcopperinordertofusethe during the closureoftheIapetus Ocean,approximately 490-390million yearsago. 53 2002). LowergradePt-Pd-dominant mineralisationhas associated copper, arsenicandnickel(GunnStyles, been proposedtoexplainthis PGEenrichmentandthe late hydrothermalprocessesfocused infaultzoneshas in azoneoftalc-carbonatealteration. Anoriginrelatedto exceed 100 ppmclosetothebasalthrustofophiolite levels intheUnstophiolite,Shetland.PtandPdboth High PGEconcentrationsoccuratseveralstratigraphical sulphides isproposedforthismineralisation. and antimonytheredistributionofearly-formed hydrothermal origininvolvingtheintroductionofarsenic associated withshearing,brittlefracturingandveining.A temperature phasewithPGEtelluridesandantimonides metal sulphidesandrarePGEsulphides;alater, low- are evident:alate-magmaticphasecomprisingbase- alkaline intrusivecomplex.Two phasesofmineralisation occurs overa2 kmstrikelengthwithintheLochBorralan belt On thenorth-westernmarginofCaledonianorogenic zone in the Upper Deveron valley near Huntly. in deformed mafic-ultramafic intrusions along a major shear Pt+Pd, also occur in clinopyroxene-bearing ultramafic rocks mineralisation in these areas. PGE enrichments, up to 280 at high temperatures in shear zones, is proposed for the origin, subsequently modified by hydrothermal reworking in contaminated and xenolithic gabbroic rocks. A magmatic the Knock intrusion, near Huntly, and at Arthrath, near Ellon, this type, with up to 0.5 g/t Pt+Pd, have been identified in magmatic nickel-copper±PGE mineralisation. Deposits of Scotland have been the major focus of exploration for The Caledonian mafic-ultramafic intrusions of north-east Significant occurrencesareshowninFigure14. stream sediments,withoutanyidentifiedbedrocksource. phases containingPGEhavebeenfoundinoverburdenand Caledonian orogenic belt:amountainousareacoveringthenorthern BritishIsles,western Scandanavia,easternGreenland andpartsofnorth-centralEurope formed 53 inScotland,PGEmineralisation,upto878 ppbPt+Pd,

ppb extensive concentrations,intherange1–2 g/ttotalPGE, widespread onRumwheretheyoccurasthin,laterally PGM assemblageshavebeenrecorded.Theyaremost north-west Scotland.Ineachcaseabundantanddiverse in theTertiary igneouscentresonRum,MullandSkyein PGM havealsobeenidentifiedinlayeredultramaficrocks association withchromitites. typical ofophiolites,dominatedbyOs,IrandRu,occursin complex. ElsewhereonUnst,PGEmineralisationmore also beenreportedinthecumulatesequenceof of PGE,blueandgreenlowconcentrations. 200 µm across.Redandyellowindicate highconcentration from SouthDevon.Notethefield ofviewisapproximately of platinum(top)andpalladium (below)inagoldgrain Figure 13Microchemicalmaps showingthedistribution www.MineralsUK.com 28 Platinum All rightsreserved. BGS100017897/2009). Figure 14Significant PGEoccurrencesandthe locationofPGErefineries inBritain. (OS topography©CrownCopyright. Sk Rum ye Mull Cowbridge Loch Bor Mauc Cor Deveron Upper ryc Crediton Thornhill Basin hline Basin S ralan outh Hams harmaig Knoc T rough k Ar Chessington Leicester thrath Acton Enfield PGE occur R oyston Unconformity-related PGE refineries Intrusion-related Ophiolite Shetland Islands 0 Harlow www.MineralsUK.com r ences 10 0 Unst 20 0 km 29 Platinum along faults and in favourable host rocks due to mixing with transportation in saline oxidising fluids with deposition genesis of the precious metal grains is attributed to metal Mauchline and Thornhill basins in southern Scotland. The South Hams and the Crediton Trough in Devon, and the from the Lower Devonian and Permo-Triassic rocks in the widespread in drainage sediments and overburden derived platinum-palladium grain (Figure 13) and discrete PGM are red-bed basins and underlying reduced strata. Complex gold- identified at the unconformable boundary between Permian In several parts of Britain, a gold-PGE association has been amounts ofiron-copper-nickel sulphides. associated withthinchromititelaminaecontainingtrace A numberofcompaniesproducerefinedPGEinBritain, Refineries reduced rocks or fluids. Comtrade). 56 tonnesofpalladiumand12rhodium(UN scrap. In2008Britainexportedover51tonnesofplatinum, a netexporterofrefinedPGE,basedontheprocessing and petrochemicalsectors.TheUKhashistoricallybeen from theelectronics,jewellery, dental,mining, chemical range ofsecondarymaterialsincludingscrapandwaste refineries inBritainwherePGEarerecoveredfromawide applications. Severalothersmallercompaniesoperate range offabricatedproductsforindustrialandmedical and componentsforfuelcells.Italsoproducesawide producer ofPGEchemicals,materialsforautocatalysts Borough ofEnfield.JohnsonMattheyisalsoamajor at RoystoninHertfordshireandBrimsdown,London of preciousmetalsfromprimarysources,withrefineries leader inthissectorbutitisalsoprominenttherefining sources (Figure13).JohnsonMattheyPlcisaglobal mostly byrecyclingspentcatalystsandothersecondary www.MineralsUK.com 30 Platinum implications. group elementdistributionintheores,andgenetic the BlackSwanarea,Yilgarn Carton,Australia.4.Platinum BARNES, SJ Mines InformationCircular the platinum-groupmetalsandchromite. J BARKER, JC,STILL,MOWATT, TC references Further readingandselected of Science, resources oftheBushveldComplex. CAWTHORN Monograph (editor) of AustraliaandPapuaNewGuinea.HughesF. 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609–622. deposit, westernChina. concentrations inthesulphideoresofJinchuanNi-Cu Controls onvariationsofplatinum-groupelement SU, S,LI,C,ZHOU,M-F, RIPLEY, EM, zhtml?c=99837&p=irol-IRHome Available fromhttp://phx.corporate-ir.net/phoenix. STILLWATER MININGCOMPANY Geology, occurrence, RathbunLake,NortheasternOntario. element mineralisationinthehydrothermalCu-Nisulphide ROWELL, WF MineralReservesResourcesStatement/ from http://www.nornik.ru/en/our_products/ NORILSK NICKEL Geology, GeochemistryandExploration.(Springer: Berlin). NALDRETT, AJ Branch oftheRussianAcademySciences,(inRussian). Estimations ofMineralResources.Novosibrsk,Siberian Information TheoryontheCostsandSystemEconomic VALTUKH, KK,KRIVENKO, AP un.org/db/ UN COMTRADE. 27–34. Passenger Cars. Breathe –ControllingDieselParticulateEmissionsfrom TWIGG , MV, and Vol. 81,1272–1277. , and . 2004.Magmaticsulphidedeposits: 2009.Available fromhttp://comtrade. Platinum MetalsReview, . 2006.[citedMarch2009].Available PHILLIPS EDGAR Mineralium Deposita, , AD.1986.Platinum-group , PR2009.CleaningtheAirWe , andR www.MineralsUK.com . 2009.Annualreport. and AVKIN Vol. 53,Pt1, QI , JC1999. , L.2008. Vol. 43, Economic This commodity profile was produced by the British Geological Survey (2009).

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