Zales mentions that white gold should have 75-percent gold composition, with the remaining 25 percent comprised of other metals like silver and palladium. Other metals like copper and zinc are also included. Diffen.com also notes a visible indicator of white gold is its highly reflective quality, and it is not subject to tarnishing. White gold is also known for its pristine shine.
White gold is usually made with rhodium coating, giving the metal its notable luster, according to About.com. Rhodium is rare member of the platinum family, Zales notes. Without rhodium plating, white gold has a yellowish color. White gold should also have the same 18K proportion as yellow gold.
According to Jewelry Secrets, another way to tell if white gold is real is the fading of the jewelry over the years. This is due to the rhodium plating wearing away over time, which requires replating every two years or so. Diffen.com notes that micro-scratching is another factor that can cause white gold to turn yellow, since micro-scratching can completely remove gold from the jewelry.
Jewelry Secrets notes that white gold is essentially yellow gold with zinc included. White gold is not a natural metal, but a man-made concoction designed to replace platinum.
White gold is normally made of palladium-gold-silver alloy or zinc-gold-nickel-copper alloy, About.com notes. Since there are people who have allergic reactions to white gold, American and European manufacturers tend to manufacture white gold without nickel. The nickel-plated variety can usually be found in older forms of white gold jewelry.