The name carat derives, via Medieval French and Italian, from Arabic qīrāṭ, meaning "bean pod," which is itself from Greek keration, referring to both the carob bean and a small weight. Early in the 20th century, the weight of the carat was set at 200 milligrams, or 0.2 grams.

Where did the carat originate from?

'Carat' is a term used to describe the weight of a diamond, and the word originates from Ceratonia siliqua, commonly known as the Carob tree. In ancient times, before scales and units of mass were invented, diamond traders compared the weight of a diamond to the seeds of the Carob tree.

Why are diamonds weighed in carats?

The carat, the standard unit of weight for diamonds and other gemstones, takes its name from the carob seed. Because these small seeds had a fairly uniform weight, early gem traders used them as counterweights in their balance scales. ... Today, a carat weighs exactly the same in every corner of the world.