What's the difference between white gold and other gold?
Dear Straight Dope:
What is the difference between white gold and any other kind of gold?
I called a few local jewelers about this and got this answer, "The difference is in the color." Uh, thanks. Being the tenacious investigative reporter that I am, I researched it a little further (found a talkative jeweler with time on his hands) and came up with this.
Gold as it comes out of the ground is a pure element that is yellow and relatively soft. That's your "24 karat gold." Many people like the yellow color of 24 karat gold, but the lack of hardness can be a disadvantage in jewelery, so it is alloyed with other metals. This affects the color in addition to the hardness. To make white gold, an alloy of palladium and nickel is added to the gold. Jewelers talk about other colors, too: add a little copper for a "pinkish" caste; if you want a "green" tint, add silver. Zinc is added to make the gold harder.
The "karat" tells how much alloy of other metals is used -- 18k gold is 75% gold and 25% alloy, 14 karat has more alloy, etc. One might think that yellow gold would always be more expensive than white because it is "purer," but that isn't necessarily true. White gold can be more expensive because it's harder to fabricate. A good gold "manufacturer" is judged by his or her ability to use the different alloys to achieve the qualities desired in jewelry. The head of a ring that holds a gemstone, for example, must be hard but also flexible, so the alloy is important there.
Just so you can really impress the girls at bridge tonight, 24k gold is 99.99% gold, 22k is 91.67% gold, and 20k is 83.33% gold. Those of such high karatage are most often used in Asia and the Middle East. Generally, 20k or higher is yellow in color. 18k is 75% gold and is the most common karatage in Europe. It's also popular in America and can be yellow or other colors. 18k white gold made with nickel is very hard. 18k yellow gold is softer than its 14k counterpart. 14k gold is most common in the USA and can be yellow or other colors. 14k white gold is harder and used in prong settings. 14k white gold has a yellowish tinge and is often plated with rhodium (a platinum group metal) to give it a white appearance. 12k gold is 50% gold and is commonly used in class rings and can be other color. 10k gold is 41.67% gold and is common in promotional goods. It's the lowest alloy that can be called gold in the US and it's very brittle.
Most of this information came from Donald Fogg, of F.D. Fogg Jewelry in Albuquerque, New Mexico -- a very kind and patient man.