History

(Sp. platina: silver) Discovered in South America by Ulloa in 1735 and by Wood in 1741. The metal was used by pre-Columbian Indians.

Sources

Platinum occurs natively, accompanied by small quantities of iridium, osmium, palladium, ruthenium, and rhodium, all belonging to the same group of metals. These are found in the alluvial deposits of the Ural mountains, of Columbia, and of certain western American states. Sperrylite, occurring with the nickel-bearing deposits of Sudbury, Ontario, is the source of a considerable amount of metal.
The large production of nickel makes up for the fact that is only one part of the platinum metals in two million parts of ore.

Properties

Platinum is a beautiful silvery-white metal, when pure, and is malleable and ductile. It has a coefficient of expansion almost equal to that of soda-lime-silica glass, and is therefore used to make sealed electrodes in glass systems. The metal does not oxidize in air at any temperature, but is corroded by halogens, cyanides, sulfur, and caustic alkalis.
It is insoluble in hydrochloric and nitric acid, but dissolves when they are mixed as aqua regia, forming chloroplatinic acid. 
A Periodic Table of the Elements at Los Alamos National Laboratory