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.
A rhodium-coated piece of jewelry may retain its finish for a lifetime or for only a short period of time depending on the article's exposure to wear and the body chemistry of the individual wearing the piece. Should the rhodium finish wear over time, it can easily and inexpensively be re-coated to its original brightness.
A karat mark is applied, because registered US trademarks are required by federal law (the National Gold and Silver Marking Act). A karat mark along with a registered US trademark will assure you that the gold is of the specified quality. Any suspected violation of this Act should be reported in writing to:
The Jewelers Vigilance Committee
401 East 34th Street, Suite N13A
New York, NY 10016
(Information provided in cooperation with Jewelers of America, Inc.)