The word carat is often mistaken with size, yet the carat is actually measured in weight. The word carat derives from the Greek word “keration” meaning fruit of the carob. The Carob tree (Ceratonia Siliqua) is an evergreen tree, with an edible pod containing seeds, which is native to the Mediterranean region. Carob seeds, surprisingly have quite a uniform weight of 0,20 grams, and therefore old civilisations used these seeds as a reference weight for precious gemstones and for weighing other small weight items. One carob seed equals one carat and therefore one carat equals 0,20 grams.
The carat, as weight, was defined with precision in 1832 in South Africa, the location with the highest production and exportation of diamonds in the world. However, the word became a metric unit only in 1907 at the Forth General Conference on Weights and Measures.
Carat weight alone does not determine a diamond’s value. Two diamonds in equal weight can vary widely in price because of quality differences. In fact, a smaller diamond may have a higher price thanks to a superior cut, clarity and colour.