Composition - Platinum ; Hardness - 4
Platinum has been used for thousands of year, but it was not recognized as a chemical element until 1735. Of the three precious metals – gold, silver, and platinum – it is the rarest and the most valuable. Chemically inert and resistant to corrosion, platinum does not tarnish when exposed to the atmosphere, unlike silver. It is silver grey, grey-white, or white in colour, opaque and has a metallic Iustre. It is slightly more dense than pure gold and about twice as dense as silver. Early jewelers had difficulty achieving the 1,773o C (3,223oF) needed to melt platinum: it is not until the 1920s that the technology was developed sufficiently to work this precious metal.
OCCURRENCE
Platinum forms in igneous rocks, usually as ores in which the grains of platinum are often too minute to be seen with the naked eye. It may also occur in secondary “placer” deposits in river sands and gravels and glacial deposits – usually as grains, more rarely as nuggets. The main occurrence of platinum have been in South Africa, Canada (Sudbury), the USA (Alaska), Russia (the River Perm and other rivers running down from the Urals), Australia, Colombia and Peru.
REMARK
Although nuggets had been set in rings before 1920, most platinum jewellery dates from after this time. Soft and easy to work, platinum is often fashioned into quite intricate designs.
