Pure gold
Pure gold (24k) is too soft to hold up under daily wear, so for most uses it has been “karated” or alloyed with other metals to make it harder and, subsequently, more durable.
Under the United States marking system, pure gold is 24k. The karat numeral represents the amount of pure gold in the alloy. For example, 10k equals 10 parts of pure gold to 14 parts of other metals, making a total of 24 parts. Under European marking systems, the numerals represent parts of pure gold in the alloyper 1000 total parts.
Standard karats of gold used in jewelry are 10k, (not made in Europe), 14k (585), 18k (750), and 22k (920). United States law prohibits any item less than 10k from being called “gold.”
During the alloying process, the color, malleability, and melting point of karated gold can be altered. Gold can be alloyed to yellow, rose, peach, pink, green, white, gray, blue, and the rarely occurring purple. Each alloy has its own distinct working properties.
Don’t confuse “karat” with “carat,” which is a unit used to denote the weight of a gemstone. The abbreviation for carat is “ct.”