Carat (mass)

The carat (symbol: ct) is a unit of mass equal to 200 milligrams (0.2 grams; 0.00705 ounces). It is used for measuring gemstones and pearls. The modern carat is sometimes also referred to as the metric carat, to distinguish it from older values.

History:

The word "carat" comes from the Greek word keration, referring to the carob seed. In ancient times, carob seeds were widely used to balance scales because they were believed to have a relatively uniform mass. This consistency, though not perfect, made them a practical standard of weight for small, valuable items like gemstones.

Throughout history, the exact weight of a carat varied slightly from region to region. In 1907, at the Fourth General Conference on Weights and Measures, the metric carat, defined as 200 milligrams, was adopted internationally to standardize the measurement.

Usage:

The carat is most commonly used to describe the weight of diamonds, but it's also employed for other gemstones such as rubies, sapphires, emeralds, and pearls. Larger carats indicate a heavier gemstone, but not necessarily a more valuable one. The value of a gemstone depends on a combination of factors including carat weight, cut, color, and clarity (often referred to as the "4 Cs" for diamonds).

Fractional carats are expressed using decimals. For example, a 0.50 carat stone weighs half a carat, or 100 milligrams. Jewellers and gemologists often use points to describe fractions of a carat, where one point equals 0.01 carat. Therefore, a 0.50 carat stone is also referred to as a 50-point stone.

Important Note:

It is crucial to remember that carat refers to mass and not size. While a higher carat weight generally corresponds to a larger stone, other factors, such as the stone's cut and density, can affect its perceived size. Two gemstones of equal carat weight can appear to be different sizes if they have different densities or have been cut differently.