Cut, Colour, Clarity and Carat are the worldwide characteristics used to classify the rarity, quality and value of diamonds. Diamonds with the highest combination of 4C ratings are the rarest and most valuable.
Carat - This is often abbreviated as “ct” and has two separate meanings:
1) It is the unit of weight measurement for gemstones, whereby one carat is equal to one-fifth of a gram. A carat is divided into points, and there are 100 points in a carat, so 25 points is equal to ¼ carat. It is one of the four characteristics that influence the value of a diamond.
2) It is the term used to describe the purity of gold alloy used in an item of jewellery. With pure gold being rated as 24 carat, the most common standards of gold alloy used in jewellery are:
- 9ct gold, which 37.5% pure gold (or 375 parts pure gold and 625 parts other metals). - 14ct gold, which is 58.5% pure gold (or 585 parts pure gold to 415 parts other metals). - 18ct gold, which is 75% pure gold (or 750 parts pure gold and 250 parts other metals). - 22ct gold, which is 91.6% pure gold (or 916 parts pure gold and 84 parts other metals).
The carat of gold used in an item of jewellery is illustrated in its hallmark (see hallmark).
Clarity - One of the four characteristics that influence the value of a diamond. A diamond’s clarity is determined by the degree to which it is free from naturally occurring inclusions, or “nature’s fingerprints”. The number, type, colour, size and position of these “birthmarks” can affect the value. However, many of these inclusions are actually invisible to the naked eye and require magnification under an eyeglass before they can be seen. The fewer the inclusions, the rarer the diamond and thus the more valuable it is.
Colour - One of the four characteristics that influence the value of a diamond. While most diamonds appear white, many of them actually display hints of colour barely discernible to the naked eye. The closer a diamond is to colourless, the rarer and more valuable it is. Diamonds with a strong pure colour are extremely rare and called “fancies”. Some of these colours that can be found in diamonds include pink, blue, yellow, green and orange.
Cut - One of the four characteristics that determine the value of a diamond, and the only one that can actually be influenced by man. When a diamond is cut well and all the facets are in proportion, light will reflect from one facet to another and disperse through the top of the stone, resulting in a display of brilliance and fire. When the facets are not in proportion or when the diamond is cut too shallow or too deep then light is not reflected and refracted adequately and the brilliance is not as great. It is this poor cutting that can severely decrease the value of a diamond. The style of cut, such as baguette, emerald or marquise, is a matter of personal taste and not so important in influencing the value of a diamond. Below are three diagrams showing how the cut of a diamond can affect the way it reflects and refracts light: