The word ‘carat’ comes from the carob seeds that early diamond traders would use when weighing their diamonds. Today, carat refers to a diamond’s weight, with one carat equal to 0.2g. Carat weight isn’t directly related to size or price: a diamond can be cut deeper or shallower, meaning two one-carat stones can have very different proportions, while price is affected by a combination of cut, colour and clarity, along with the carat weight. Furthermore, certain carat weights – such as one or two carats – are in greater demand, so their price is disproportionately higher than slightly lighter or slightly heavier stones.