Understanding the 4 C's - Carat

Unlocking the Mysteries of the 4 C's: Carat, Cut, Colour, and Clarity in Diamonds - By Melissa Holt DGA

When it comes to gemstones, particularly diamonds, there's a lot of talk about the famous 4 C's: Carat, Cut, Colour, and Clarity. These four aspects are the fundamental criteria used to grade and evaluate diamonds, and they were introduced by the Gemmological Institute of America (GIA) in the 1960s.

In this article, let's delve into the first C - Carat.

Understanding Carat:

Often misunderstood, the Carat of a diamond does not refer to its size, but rather to its weight. Throughout history, gemstones have been prized and valued based on their weight, with higher carat weights indicating greater desirability and impressiveness. However, it's crucial to remember that carat weight is just one piece of the puzzle. To truly gauge a diamond's worth and compare it with others, it must be evaluated alongside the other C's - Colour, Clarity, and Cut.

Unravelling Total Carat Weight:

 When shopping for jewellery, you'll often come across the term "total carat weight" as a distinguishing feature. Total carat weight refers to the combined carat weight of all the diamonds in a piece. This can sometimes be misleading for buyers when comparing different pieces. As a general rule, a piece with many small stones might have the same carat weight as another piece with a single, larger stone, but its value may differ significantly. Thus, it's essential not to be swayed by carat weight alone.

Putting Carat in Perspective:

One carat is equivalent to 0.2 grams, and diamonds are also measured in points, with 100 points making up one carat. For instance, if a ring is described as 70 points, it equals 0.70 carats, while a 50-point stone would be 0.50 carats or half a carat.

The Origins of "Carat":

 The term "Carat" is believed to have originated from the use of Carob seeds in ancient times. The Latin name for the Carob tree, "Ceratonia Selequia," or "Keration" in Greek, likely gave rise to the word "Carat." Before modern weighing methods, Carob seeds were often used to compare against the weight of diamonds due to their uniform size and weight, which is approximately 0.20 grams or equivalent to one carat. These seeds were convenient as a simple counterbalance on scales, especially in remote areas where diamonds were discovered.

The Role of Cut in Carat Perception:

 One reason why stones of the same carat weight may look different lies in their cut. The Cut of a diamond affects its appearance, with a shallower cut making the stone appear larger in width and a deeper cut causing it to spread smaller. A well-balanced cut and proportion are vital to allow light to refract properly within the stone, giving it that captivating sparkle. Additionally, for fancy-shaped diamonds, the carat weight can significantly impact their appearance, with elongated shapes like ovals appearing larger than round brilliant cuts of the same carat weight. Consequently, certain shapes may command a premium due to this visual effect.

Carat Weights and Different Gemstones:

 Despite having the same weight of 0.2 grams, different gemstones can appear significantly different in size. This is because they possess different Specific Gravity values and densities. For instance, diamonds have a Specific Gravity of 3.52, meaning they are 3.5 times heavier than an equal volume of water. As a result, a 1-carat sapphire will appear smaller than a 1-carat diamond, due to the sapphire's higher density. This difference is particularly useful when examining diamond simulants, as it can aid in distinguishing them from real diamonds.

Carat vs. Karat:

It's important to differentiate between "Carat" and "Karat." Carat refers to gemstone weight, while Karat is used to describe the purity of metals in jewellery, such as 18 Karat gold.

The Significance of Carat:

Carat weight is undoubtedly an important factor to consider when evaluating diamonds, but it's only meaningful when evaluated alongside the other 4 C's. Together, they play a vital role in determining a diamond's value and desirability.


If you have any further questions about the carat weight of your stones or any other aspect of diamonds, feel free to get in touch with us at email@holtsjewellery.co.uk

We'd be delighted to assist you in your quest for the perfect piece of jewellery.