Rhodium
Rhodium is a rare, silvery-white, very hard, member of the platinum group of precious metals. Atomic symbol Rh and atomic number 45. Although it is a very hard metal, it is also brittle and difficult to work with. This is why it is not considered a feasible material to make solid jewellery from.
Being both scratch and tarnish resistant, rhodium is typically used for the plating of jewellery. It is also highly valued for its white, mirror-like quality, which enhances any diamonds scintillation and colour in jewellery items. White gold rings will typically have rhodium plating to keep the piece shinny longer and prevent tarnishing and scratches.