Rhodium is a chemical element that has been assigned the symbol Rh. Its primary use is in catalytic converters for motor vehicles … however, we use it every day in the jewelry industry. Here’s how:
When a white gold jewelry piece is new, Rhodium is electroplated onto the item to give it a bright white and reflective surface.
In white gold some of the alloys are nickel or palladium (both white metals). This makes the gold have a creamy white color to the metal. In some light, the natural white gold will have a yellowish tint. However, when you put it next to a yellow gold piece, the white piece definitely looks white. The higher the gold content, the more yellow it will appear. Non-Plated 18kt white gold will look more yellow than a 10kt white gold item. Rhodium finishes the process, and while it’s on the surface, can make the karat of gold indistinguishable… they’ll all have a bright silver mirror-finish!
Pure rhodium jewelry is exceptionally rare and expensive, as it’s very difficult to fabricate (due to poor malleability) and has such a high melting point that I have never seen any. It wouldn’t be my choice to have a fine ring made out of.
Because of rhodium’s high price, silver (which tarnishes quickly) is usually coated/plated with imitation rhodium to slow the discoloration process. The downside of this, however, is it makes it impossible to size or polish the silver jewelry without the other layers showing through.