A measure of the purity of gold, pure gold being 24 karats.
A karat is a measure of purity, when referring to gold. You may have seen different types of jewelry referred to as 14-karat gold or 18-karat gold, but are wondering what that means, especially in relation to jewelry, and what is the highest karat gold that exists?
Pure gold is known as 24-karat gold. Gold is a fairly soft metal, though, so it is mixed with other metals, such as copper or silver, to form an alloy that can be used to make jewelry. Jewelry made of pure gold can be easily bent and scratched.
A karat is a unit of fineness for gold, equal to ¹/₂₄ part of pure gold in an alloy, so an 18-karat gold ring would be made with 18 parts gold and 6 parts of another metal.
The amount of gold in jewelry greatly affects its value. For example, 18-karat gold is 75% gold, while 10-karat gold is less than 50% gold. So, a ring made of 10-karat gold, vs. an identical one made of 18-karat, would be drastically different in price.
So how did the measurement of karat come about? Over 1,000 years ago, a German gold coin called a “mark” was common. It happened to weigh 24 carats, (4.8 grams), and was pure gold. It was decided to describe the purity of the gold in the coin based upon its weight, (in carats), and over time changed the “c" in “carat" to a “k" to distinguish between the two different measurements.
In the United States, the Federal Trade Commission (FTC) sets the rules for marking jewelry with a karat value. Under FTC regulations, jewelry that is 10-karat or greater, should be stamped with either a “K" or “Kt."
So what does all this talk about carats and karats mean when it comes to gemstones and gold? Does it have anything to do with those tasty orange vegetables that grow in the ground?
Nope! Carats and karats are completely unrelated to carrots. And even though they can both be used to describe different types of jewelry, carats and karats measure completely different things!