h Africa alone is believed to hold around 63 percent of the world’s PGM reserves , which equates to nearly 63 million kilograms of the precious metals. This figure places South Africa at the top of the world reserve list for PGM. Russia captures the number two spot with a mere 6.9 million kilograms of reserves, while the United States follows in third with about 800,000 kilograms. These figures indicate that the supply of platinum and its PGM counterparts will be unlikely to run out in the near future.Aside from small alluvial deposits of platinum, practically no ores exist where platinum is the major metal. Usually, platinum based minerals are widely dispersed in sulfide ores such as pentlandite [(Ni, Fe)9S8], laurite (RuS2), irarsite [(Ir, Ru, Rh, Pt)AsS], osmiridium (Ir, Os), cooperite (PtS), and braggite [(Pt, Pd)S]. (Brittanica, Platinum Group) Most of the major platinum deposits are exploited through underground mining techniques. As mentioned prior, basically all platinum group metals are extracted from copper or nickel sulfide minerals that are concentrated by floatation separation. Smelting of the concentrate produces a matte that is filtered of copper and nickel sulfides in an autoclave. (Brittanica, Platinum Group) The filtered material is composed of 15 to 20 percent platinum group metals.Of all metals, the platinum group is among the most difficult and time consuming to separate from ore. Separation of platinum ores traditionally begins with a mineral concentrate as described above, in a process called “individual solubilization.” The concentrate is leached with aqua regia (Brittanica, Platinum Group), that dissolves the platinum (and palladium) and leaves other metals in solid form. Using ammonium chloride, the platinum is precipitated from solution, and the ensuing platinum salt is captured by filtration and heated to form a metallic powder. The powder is then redissolved in aqua regia and reprecipitated...
