Gold Quality - gold's purity is measured in karats. Pure gold is 24 karats which is very soft. To give it strength 24 karat gold is alloyed with other metals. The most common alloys used are silver, copper, nickel and zinc. The following list represents the percentage of gold along with its quality mark for the U.S. and Europe:
18 karat - 18 parts gold (75%) = 18k U.S. or 750 Europe
14 karat - 14 parts gold (58%) = 14k U.S. or 585 Europe
10 karat - 10 parts gold (42%) = 10k U.S. or 417 Europe
10 karat is the legal karat limit for alloyed jewelry metals to still be considered gold in the United States.
Different Colors of Gold
Gold jewelry comes in many different colors. Most people are familiar with yellow, white and pink (rose) gold. Below is a list of different colors of gold and their alloys.
Yellow:
18k & 14k - gold, silver and copper
10k - gold, silver, copper and zinc
White:
18k, 14k & 10k - gold, copper, nickel, zinc or gold and palladium
Pink (Rose):
18k, 14K & 10k - gold, silver and copper
Green:
18k - gold and silver
14k - gold, silver and copper
10k - gold and silver
Blue:
18k - gold and iron
Platinum
Platinum is a silvery-white metal. It is often abbreviated as Plat when stamped on a piece of jewelry. Most platinum jewelry (not all) is alloyed with iridium (which is in the platinum group of metals) to give it strength. One of the most common purities in platinum jewelry is .900. This may also be found stamped on a piece of jewelry. This is known as the quality mark. This .900 means that the item is 90% platinum and 10% iridium. Sometimes you will find both marks stamped like this 10% Irid Plat (meaning there is 10% iridium and 90% platinum).