Platinum group metals minerals

Platinum Group Metals in Mineral Commodity Summaries 1992 U.S. Bureau of Miaes, Washington, D.C., 1992. 

Osmium occurs in nature, always associated with other platinum group metals. It usually is found in lesser abundance than other noble metals. Its most important mineral is osmiridium (or iridosmine), a naturaUy occurring mineral alloyed with iridium. 

The initial steps are similar to any other mineral extraction process. This involves crushing mineral, froth flotation, gravity concentration and other steps to obtain platinum metal concentrates that may contain about 30 to 40 wt% of platinum group metals. The concentrate is treated with aqua regia to separate soluble metals, gold, platinum, and palladium from other noble metals such as ruthenium, rhodium, iridium, osmium, and silver that remain in... 

FIGURE 21.2 Primary mineral sources of metals. The s-block metals occur as chlorides, silicates, and carbonates. The d- and p-block metals are found as oxides and sulfides, except for the group 3B metals, which occur as phosphates, and the platinum-group metals and gold, which occur in uncombined form. There is no mineral source of technetium (Tc in group 7B), a radioactive element that is made in nuclear reactors. 

The platinum-group metals consist of ruthenium, rhodium, palladium, osmium, iridium, and platinum. Each of the metals occurs naturally in its native form, and in economically exploitable deposits the elements occur overwhelmingly as individual platinum-group mineral (PGM) species. Mutual substitution of the various PGE is common, but substitutions in other minerals, such as base-metal sulfides, typically occur to only a limited extent. A comprehensive review of PGM and PGE geochemistry is given by Cabri (2002). 

H. E. Hilliard, Platinum-group metals. U.S. Geological Survey, Minerals Yearbook 2003, 2004. on-line, http //minerals.usgs.gov/ minerals/pubs/commodity/platinum/. 

Hillard HE (1999) Metals Prices in the United States through 1998 — Platinum Group Metals, Spedal Publication USGS, 99 -109 available at http // minerals.usgs.gov/minerals/pubs/commodity/ platinum/550798.pdf... 

Hillard HE (2000) Platinum-Group Metals, U.S. Geological Survey Minerals Yearbook. 

The platinum-group metals (Ru, Os, Rh, Ir, Pd and Pt) are rare (Figure 23.1) and expensive, and occur together either native or in sulfide ores of Cu and Ni. Three sites of mineral deposits in the former Soviet Union, Canada and South Africa hold the world s reserves. The main source of ruthenium is from wastes from Ni refining, e.g. from pentlandite, (Fe,Ni)S. Osmium and iridium occur in osmiridium, a native alloy with variable composition 15-40% osmium and 80-50% iridium. Rhodium occurs in native platinum and in pyrrhotite ores (Fei S, n = 0-0.2, often with <5% Ni). Native platinum is of variable composition but may contain as much as 86% Pt, other... 

The platinum group metals occur jointly as alloys and as mineral compounds in placer deposits of varying compositions. Ru and Os are separated from the PGM mix by distillation of their volatile oxides, whereas platinum, iridium, palladium, and rhodium are separated by repeated solution and precipitation as complex PGM chlorides, or by solvent extraction and thermal decomposition to sponge or powder. PGM scrap is recycled by melting with collector metals (lead, iron, or copper) followed by element-specific extraction. 

Natural occurrence. Rhodium is one of the rarest element in the Earth s crust with an abundance of 1 pg/kg (i.e., ppb wt.). Rhodium occurs in nature as a native metal along with other platinum-group metals in the native mineral iridosmine or in sulfide ores such as rhodite, sperrylite, and some copper-nickel ores. 

With the exception of gold and the platinum-group metals (Ru, Rh, Pd, Os, Ir, and Pt), most metallic elements are found in nature in solid inorganic compounds called minerals. Table 23.1 lists the principal mineral sources of several common metals, three of which are shown in Figure 23.2 . Notice that minerals are identified by common names rather tlian by chemical names. Names of minerals are usually based on the locations where they were discovered, the person who discovered them, or some characteristic such as color. The name inalachite, for example, comes from the Greek word malache, the name of a type of tree whose leaves are the color of the mineral. 

Strickland K, Miner E, Jia Q, Tylus U, Ramaswamy N, Liang W, Sougrati M-T, Jaouen F, Mukeijee S (2015) Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal-nitrogen coordination. Nat Common 6 7343... 

Most important mineral Ruthenium is a PGM (platinum group metal). It is mainly found alloyed with other platinum metals, from which it is recovered commercially. In the PGM deposits in the South African Merensky Reef the ruthenium content (relative to the total PGM quantity) is 8%, in the Canadian Sudbury and Russian Norilsk deposits 3% and 2% respectively. 

Weathering, washing and transport of primary deposits formed alluvial deposits of platinum group metals. Platinum and other heavy metals and minerals were concentrated in clay and sand. Secondary deposits occur in the Urals and Colombia. Os-miridium, originally found in Russia, is nowadays mainly obtained along with secondary deposits of gold in Alaska and in Witwatersrand in South Africa. 

A. F. Forcroy and N. L Vauquelin. Ann. Chim. 1803, 48,177-183 D. Reilly, Richard Chenevix (1774-1839) and the Discovery of Palladium, Journal of Chemical Education, 1955, 32, 37-39 Henry E. Hilliard, Platinum-group metals chapter in Mineral Commodity Summaries 2002, uses, Reston, VA, pp. 124-125, and Platinum-group metals chapter in Minerals Yearbook 2000, Vol. I,... 

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