Diamond grading
The Four Cs
Diamonds are graded based on the 'Four Cs' - four different factors considered as important in determining the quality and worth of the diamond. This grading system allows for easy comparison of different diamonds.
The Four Cs are colour, cut, carat and clarity. The colour refers to the degree to which the diamond is white (colourless) or whether it has any yellow tone. The cut refers to both the overall shape of the diamond and the precise details of its facets. Carat is the diamond's weight, and clarity tells you whether there are imperfections (or 'inclusions') in the diamond.
With the exception of the cut, all the other Cs are naturally occuring properties of the diamond.
Free resources
Download and print our free diamond grading chart.
Download and print our actual diamond size guide.
Colour
Diamond grading will certify the stone's colour from D to Z. D is colourless - a true white diamond. As the gradings progress through the alphabet to Z, the diamonds take on a yellowish tone. Anything up to colour H is considered white, with a hint of yellow appearing in diamonds graded from I onwards.
Colourless (white) diamonds are the rarest, and therefore the most valuable. Diamonds with colour grades towards the Z (yellow) end of the scale should not be confused with 'yellow diamonds', which are a separate commodity with their own characteristics and grading scales.
Diamond grades D and E are described as 'exceptional white', F and G are 'rare white' where only a trained gemologist could find even a hint of yellow, and H is 'white' where no yellow will be detected.
Cut
Cut is the only one of the 4Cs that is influenced by the human hand. The rest (colour, clarity, carat) are created naturally as diamonds form in the earth.
Diamond cutting requires great skill and training. The cutter must polish tiny surfaces known as facets onto the rough diamond. This process is what creates the facets known as the crown, culet, table, girdle and pavilion of the diamond.
The facets, when arranged in precise proportions, will maximize the fire life and brilliance of a diamond. To cut a diamond perfectly, a craftsman will often need to cut away more than 50% of the rough diamond.
Carat
Carat is often confused with size even though it is actually a measure of weight. The cut of a diamond can make it appear much larger or smaller than its actual weight.
High carat diamonds often appear to be brighter or more brilliant than their lower carat siblings due to the prism effect of light travelling over larger distances. However, carat is merely one of the factors to take into consideration when appraising the quality of the stone.
One carat (not to be confused with Karat—the measure of purity of gold) is the equivalent of 200 milligrams. One carat can also be divided into 100 "points." A 0.75 carat diamond is the same as a 75-points or a 3/4 carat diamond.
The term carat is a derivative of the word carob. Carob seeds, which are surprisingly uniform in weight, were used as a reference for diamond weight in ancient civilizations. One carob seed equalled one carat.
It is often assumed that a 1-carat diamond costs exactly twice the price of a 1/2-carat diamond. This is not the case. Since larger diamonds are found less frequently in nature, a 1-carat diamond will cost much more than twice as much as a 1/2-carat diamond, assuming colour, clarity and cut remain constant.
Clarity
Diamonds have natural blemishes in their make-up. Minerals or fractures form these tiny faults, or inclusions, while the diamond is formed in the earth.
When light enters a diamond, it is reflected and refracted out. If there is anything disrupting the flow of light in the diamond, such as an inclusion, a proportion of the light reflected would be lost.
Most inclusions are not visible to the naked eye unless magnified.
Inclusions are ranked on a scale of perfection, or clarity, which ranges from FL (No visible characteristics under magnification) to I (Characteristics visible with the naked eye). This grading method rates diamonds on the size, nature and positioning of the birthmarks and requires an expert eye to assess.
To view inclusions, trained gemologists use a magnifying loupe. This tool allows experts to see a diamond at 10x its actual size. Even with a loupe, the birthmarks in the VVS (Very, Very Slightly Included) to VS (Very Slightly Included) range can be very difficult to find. It is only when a diamond is graded 'I' that it is possible to see the birthmarks with the naked eye.
What's the difference between VVS1 and VVS2 or SI1 and SI2? The numbers represent levels within each grade. The 1s will be cleaner (have fewer or smaller inclusions) than the 2s. This allows for more precise grading categories.
As with real birthmarks, inclusions appear as different shapes, such as crystals, clouds or feathers. These idiosyncrasies often add to the overall character of the diamond.
The majority of these natural birthmarks are invisible to the naked eye, yet they affect the way light is reflected and refracted within the stone. Diamonds that have no inclusions under magnification are extremely rare and are rated FL for flawless.
The position of inclusions can affect the value of a diamond. You may not notice a significant difference between an SI 1 and a SI 2. However, you should consider the number, size, brightness, nature and position of the inclusions.
A mounting, thus having little effect on the beauty of a diamond, can hide some inclusions. An inclusion in the middle or top of a diamond, however, could impact the dispersion of light, sometimes making the diamond less brilliant.
Our diamonds
The minimum diamond quality used for our wedding rings is a colour H and clarity Si2 unless specified otherwise.
More information
We've put together some more useful pages on such things as Diamond Fluorescence, Buying Diamonds, and Caring for your Diamonds.