Platinum
Platinum is a chemical element with symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name is derived from the Spanish term "platino", meaning "little silver".
Platinum sterling
The platinum is used to replace at least some of the copper present in a typical sterling silver alloy, which provides a greater light reflectivity (by refining the grain structure) and resistance to tarnish (thought to be caused by oxidation of copper) than standard sterling silver.