The Diamond Carat System

A carat is the unit of measurement used to describe the weight of a diamond and it is a common misconception that carat refers to size. 1 carat is defined as 200 milligrams, and 1 carat is then subdivided into 100 points for stones that weigh less than this. The term ‘carat’ finds its origins in the carob seeds that were used by early gem traders as a counterweight in their scales. This term has been in use since the 1500s and is recognised globally as a way of describing the weight of gemstones.

There are certain weight boundaries, such as 1.00 carat, 2.00 carats, etc, that cause the value of a diamond to increase significantly. For example, a 0.97 carat diamond and a 1.02 carat diamond that are the same quality will look nearly identical, however you will pay a much higher sum for the second diamond. These boundaries are aligned with ‘popular’ weights, which in turn increases demand and therefore cost.

When it comes to an antique diamond, these will have been hand-cut with their unique characteristics in mind, and so they may have different proportions to a modern laser cut stone. Therefore, it is quite usual for an antique diamond to look either larger or smaller than its modern equivalent of the same size, as these are all cut in a very standardised way.

Of course, the value of a diamond will also depend on other factors, such as colour and clarity, whether it is signed, and the design and craftsmanship of the piece itself. Carat weight alone is not the sole determination of value.