We’ve also produced separate guides on how to invest in gold, silver and platinum. Iridium: one of the densest and most corrosion-resistant metals, used in spark plugs, electrical contacts and other industrial processes.Rhodium: one of the rarest and most expensive precious metals, used for catalytic converters and plating jewellery.However, the following metals are sometimes included in the precious metal category: Palladium: also used in catalytic converters, as well as electronics and jewellery.Platinum: in high demand for automotive catalytic converters thanks to its density and resistance to corrosion, in addition to jewellery and medical products such as chemotherapy drugs.
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