Rhodium

Rhodium is a hard, silvery-white metal belonging to the platinum family of metals. It is a chemical element with the symbol Rh and atomic number 45 in the periodic table. Rhodium is usually found in platinum ore. 

Rhodium is extremely resistant to corrosion and cannot be attacked by acids. The primary use of rhodium is as a hardening agent in platinum and palladium alloys used in making, amongst other things, spark plugs and laboratory crucibles. Rhodium plating is also used on white gold and platinum jewelry to give it a relective white surface.