A rare metallic element of the platinum group. It is similar to platinum, being silver-white, malleable, ductile, and in ordinary conditions non-tarnishable, but it is much lighter in weight. It is used in jewelry alone or as palladium alloy, as a less expensive substitute for platinum.
It was discovered in 1803 by William Hyde Wollaston and names by him after Pallas, a newly discovered asteroid. Palladium is often used today, because of its being lighter and cheaper than platinum, to make wedding rings and jewelry that can be worn without 'drag' on dresses of silk or lightweight materials.
From: An Illustrated Dictionary of Jewelry, autor: Harold Newman, publishers: Thames and Hudson