Carat, Karat or Carrot?

Since entering the world of precious metals, I have wondered about some of the terminology and how it came to be.  I had always thought “carat” and “karat” were interchangeable but I quickly found out that this is not the case.

karat gold
Carat, Karat, Carrot?

A Carat is a unit of weight.  It’s used to describe diamonds and other precious gemstones, such as pearls.  One carat is equal to 200 milligrams, which is the same as 0.2 grams. A two carat diamond would was 400 milligrams (0.4 grams).

A karat, on the other hand, is a measure of purity when referring to gold. You may have seen different types of jewelry referred to as 14 karat or 18 karat gold. What does that mean and what’s the highest karat gold that exists?

Pure gold is known as 24-karat gold, Gold is a fairly soft metal so it’s not often used to make jewelry in the US. However, in certain countries 24 karat gold is quite popular.  Jewelry made of pure gold can be easily bent and scratched.

Gold is often mixed with other metals, such as copper or silver, to form an alloy that can be used to make jewelry.  A karat is equal to 1/24th of pure gold, so an 18-karat gold ring would be made with 18 parts gold and 6 parts of another metal.

Gold Fineness Chart
Gold Fineness chart

The amount of gold in jewelry affects its value greatly.  For example, 10-karat gold jewelry is less than half gold.  On the other hand, 18-karat gold is 75% gold. The purest gold jewelry commonly available is 18 karat gold, and is usually much more expensive than lower- karat varieties.

So how did such a measurement of purity come about? Over 1,000 years ago, a German gold coin called a “mark” was very common. It happened to weigh 24 carats (4.8 grams) and was pure gold.  People 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 the two different measurements.