Rhodium is not used in jewelry as such, ie, there is not jewelry made of rhodium. It is used to bathe pieces of silver and white gold to perpetuate the silvery sheen of them, avoiding the darkening of the first and yellowing of the latter.

Rhodium in jewelry (Source: http://guia.mercadolibre.com.mx)

Rhodium is a metal ductile and silvery white. It not dissolves in acids, even in aqua regia, though finely divided if that can be dissolved in it, and also in concentrated sulfuric acid and hot.

Rhodium has a higher melting point than platinum and a lower density. Like all platinum group metals, or PGM'S (PLATINUM GROUP METALS), is a powerful catalyst. Used in combination with platinum is used to produce nitric acid from ammonia, is also used as a reflective base in high-end vehicle headlights for its intense brightness and its characteristic of being steel up in acidic media.

Rhodium is the most important metal in the PGM's, because of their rarity in nature reaches high prices, but has not yet discovered all industrial applications that have this metal.

Rhodium is an element used in jewelry. Typically, white gold is galvanized with a layer of rhodium from 0.05 to 0.5 microns thick. The thickness so small scratches in this layer may allow the oxidation and this weakened layer of rhodium. Ideally, a layer of 2.0 micron to last longer. A white gold jewelry can be plated with rhodium again in some jewelry shops.

Rhodium is easily galvanized to form a hard surface, resistant to wear and permanent shine, used both in stationary electrical contacts (mirrors and reflectors), and as a product for finishing the pieces of jewelry.

For all the foregoing, the rhodium-plated jewelry is durable, resistant to rust and corrosion with a brilliance that hardly get into other jewelry in the same price.

Rhodium bath for jewels (Source: Guide for Designers and specifiers from Jewelry Design Technology Andaluz Centre).

Rhodium bath is the application of a bath of rhodium to give items a bright white tone with which enhances brightness and color.

Processes (plating or chemical) are to be deposited, electrochemically, thin metal layers on the surface of a piece submerged in a solution of metal ions or electrolyte. In this processes are used relatively pure chemicals, salts and metals, so that during operation the metals are deposited on the pieces completely.

This technique, called electroplating is generally used in the manufacture of baths gold, rhodium or silver.