Gemstone Size and Weight


A carat, as a unit of weight, originally comes from the Arabic qirat which was roughly the weight of 4 grains and was traditionally used to weigh small amounts.

Dictionary Definition

A unit of weight in gemstones, 200 milligrams (about 3 grains of troy or avoirdupois weight). Abbreviation: c., ct.

Originally, carats weights were only used to measure diamonds but carats have now become the accepted unit of measurement for gemstones as well.

The weight of a gemstone does not necessarily correspond to its size. The reason for this is that difference gemstones have different densities. A one carat round cut ruby will not have exactly the same measurements as a one carat round cut sapphire or emerald because of their different relative densities.

Carat Total Weight

Total carat weight ( is the weight of all the gemstones in an item of jewelry added together.



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