Carats and KaratsThe term carat is used as both a unit of mass - especially for gemstones - and as a measure of purity for gold. In the United States and Canada these terms are spelled differently - as carat and karat respectively - to avoid confusion. But many people get them confused anyway.
Interestingly, the term karat was also derived from the name for the carob seed. So how did the weight of the carob seed relate to the purity of gold, and why is pure gold defined as "24 karat"? A precise answer is not easy to find, but the connection appears to have originated from the Roman Emperor Constantine, who introduced a gold coin that was equal to 24 carob seeds in weight.
Here in Thailand, like in most Asian countries, gold is very important as a medium of exchange and a store of wealth. The Thais still use a traditional measurement of weight for gold, the "baht." This term can be a bit confusing for foreigners, since the Thai currency is also called the baht. One baht of gold is equal to 15.2 grams, slightly less than half of a troy ounce (16.2 grams). Fortunately for the gemstone industry, nearly the entire world is standardized, with the carat being the accepted measurement of weight for gemstones. We do occasionally get requests for gemstones measured in rattis, an Indian measurement where 1 standard ratti is 182 mg. But the main confusion any gem dealer encounters with carats is the inexperienced buyer who thinks of the carat as a size measurement. Varieties of gemstones differ considerably in their density or specific gravity, and the cut also affects how large a gemstone appears when viewed face up. Always check the dimensions in millimeters when you're buying a gemstone and don't rely on the carat weight alone. |
- First Published: April-25-2008
- Last Updated: January-22-2019
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