When you’re shopping for diamond jewelry, you’ll need to know your carats from your karats. What does each mean? What’s the difference between 10-karat and 24-karat gold? Carat and karat to many sound like the same thing, but in fact they are totally separate terms, and in the jewelry world you have to know the difference.
Carat vs karat: What is the difference?
Diamond carat (ct) is the globally recognized standard for the weight of a diamond or gemstone. One carat weighs 0.20 grams. Karat is a measure of the purity of gold. 24-karat gold - is pure gold with zero impurities. By comparison, 10-karat gold is 41.7 percent gold and 58.3 percent base metals or impurities. -Webster Dictionary
What you need to know about diamond carat
A metric “carat” is defined as 200 milligrams. Each carat is subdivided into 100 ‘points.’ This allows very precise measurements to the hundredth decimal place. A jeweler may describe the weight of a diamond below one carat by its ‘points’ alone. For instance, the jeweler may refer to a diamond that weighs 0.25 carats as a ‘twenty-five pointer.’ Diamond weights greater than one carat are expressed in carats and decimals. A 1.08 carat stone would be described as ‘one point oh eight carats.’
All else being equal, diamond price increases with diamond carat weight because larger diamonds are rarer and more desirable. However, two diamonds of equal carat weight can have very different values (and prices) depending on three other factors of the diamond 4Cs: Color, Clarity, and Cut.
While now you know what carat means, it’s also important to remember that a diamond’s value is determined using all of the 4Cs, and not just carat weight. -GIA
What you need to know about gold karat
Karat, also spelled Carat, a measure of the fineness (i.e., purity) of gold. It is spelled carat outside the United States but should not be confused with the unit used to measure the weight of gems, also called carat. A gold karat is 1/24 part, or 4.1667 percent, of the whole, and the purity of a gold alloy is expressed as the number of these parts of gold it contains. Thus, an object that contains 16 parts gold and 8 parts alloying metal is 16-karat gold, and pure gold is 24-karat gold.
This system of indicating the relative proportion of gold originated with a medieval coin called a mark. A mark weighed 24 carats (in this case, the carat was the same as that used in the weighing of gems and was theoretically equal to the weight of the seed of the coral tree). Pure gold could not be used to produce marks because it was too soft, so copper or other metals were added to produce a hard alloy; the purity of the coin was then expressed by the proportion of its carat weight that was actually contributed by gold. -Britannica