White gold is an alloy, or mixture, of the element gold and other precious and base metals such as palladium, silver, platinum and nickel. Because the natural color of gold is yellow in tone, gold must be combined with a white metal to give a relatively white appearance.
The color of white gold shows subtle differences due to the variety and/or type of gold alloys. In fact, not only does white gold exist with the addition of other metals but gold may be "colored" with other elements to produce exotic gold hues such as green, blue, brown and purple. Every refiner or manufacturer of white gold has a proprietary "recipe" that is considered to be the best.
To keep the white color consistent and bright, white gold jewelry is generally coated with rhodium. Rhodium is an elemental, non-tarnishing member of the platinum group of metals (rethenium, rhodium, palladium, osmium, iridium and platninum) that is very white, highly reflective and extremely durable. While rhodium coating provides a bright, hard finish, it is not impervious to the effects of wear and abrasion that occur with everyday use.