By
Ashley Bailey 
, Wednesday, August 02, 2006 12:00 AM
Gold is the technicolor metal, available in six hues: yellow, white, pink (or rose), green, blue and gray. And it's been available in a variety of colors since at least the Third Millennium BC when Persian artisans used inlays of colored gold for contrast.
So don't just think of gold as a yellow metal.
Unlike platinum or silver, which tend to be used in very pure form, gold can be as little as 41.7% pure and still be legally marked and sold as gold in America. Here's why:
Gold is a very soft metal and needs the addition of other metals like silver and copper to give it greater hardness. Gold purity is stated in "karats"
(not to be confused with carats, a unit of weight for gems), with 24 karats equal to 100% pure gold. The gold purity most consumers buy is either 18 karats (75% pure) or 14 karats (58.3% pure). Gold that is 10 karats (41.7% pure) is popular for less expensive jewelry. These purities are stamped on the jewelry as appropriate: 24 kt., 18 kt., 14 kt., and 10 kt.
Colored gold is commonly made in alloys up to 18 karats (3/4s pure gold).
To achieve different colors and purities, refiners mix in different metals in different ratios. The more alloy, the darker or more pronounced the color.
Here's a chart of the most common ingredients added to get different colors alloys.
COLOR MOST COMMON ADDITIVES
Yellow gold silver and copper
White gold Nickel, zinc, copper, tin and manganese
Pink gold Mostly copper with some silver
Green gold Mostly silver or cadmium
Blue gold Iron
Gray gold Iron
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