Carat
Carat is the unit measure of weight of a gemstone. The name carat is derived from the name of the ‘carob’ or locust tree found in Mediterranean lands. The dried seeds of this tree were once used by traders as a unit of weight for gems because the seeds have a remarkably consistent weight.
One carat is equal to a fifth of a gramme. One carat is divided into 100 points, so 50 points = half a carat and 25 points = a quarter carat.
In terms of desirability, the other C’s being equal, the heavier the diamond the higher the price per carat. However, this works on a non-linear scale, therefore larger diamonds are proportionally much more valuable. For example a diamond that is twice the weight of another will be more than twice the price – as it is more than twice as rare. This scale also jumps at certain points which are more popular such as 0.5ct and 1ct.
Clarity
Diamonds are also graded on their clarity, or freedom from inclusions and blemishes. It is much rarer to find a stone without natural marks, blemishes or signs of growth.
Clarity is graded in the laboratory under 10x magnification by an experienced grader, this is the results:
| Flawless | FL | Show no inclusions or blemishes |
| Internally Flawless | IF | Show no inclusions and only insignificant blemishes |
| Very Very Small Inclusions | VVS1/2 | Contain minute inclusions that are difficult to see and locate |
| Very Small Inclusions | VS1/2 | Contain minor inclusions that are somewhat difficult to see |
| Slightly Included | SI1/2 | Contain noticeable inclusions that are easy to see |
| Imperfect Seen | I1/2/3 | Contain obvious inclusions that can easily be seen with the naked eye |
Please note the numerical reference after the clarity grade denotes the possible, nature, size, number and position of the inclusions so that those with a number one grade are more likely to be smaller, whiter and located on the outer part of the diamond.
Colour
In terms of colour diamonds can appear on two scales, either ‘white diamonds’ or ‘fancy colours’.
Firstly diamonds are valued for their lack of colour or the ‘degree of whiteness’. The desirability and value of a ‘white’ diamond increases as the depth of hue decreases. We grade these on an alphabetical scale in comparison to a set of Master-stones. On a grading scale that starts at D and goes all the way down to Z we only stock diamonds that are G or above.
GRADE |
DEFINITION |
GENERAL APPEARANCE |
| D | Exceptionally White + | Face up and face down colourless |
| E | Exceptionally White | |
| F | Rare White + | |
| G | Rare White | |
| H | White | Face up colourless, face down slightly tinted |
| I/J | Slightly Tinted White | |
| K/L | Tinted White | Face up slightly tinted, face down obviously tinted |
| M-Z | Tinted Colour | Face up and face down obviously tinted |
| Fancy | Fancy Colour | Face up definite colour |
For fancy coloured diamonds the grading is reversed; so it is the ‘saturation of colour’ that is prized. Fancy colours include yellow and brown, sometimes green, pink and blue and the exceedingly rare red and purple. The value of fancy colours is also determined by fashion as well as rarity.
Each colour grade represents a ‘spread’ or range of colour not just one point along the colour series. The point of division between each colour grader in any of the colour grading systems is an entirely arbitrary point we therefore grade in exceptionally controlled conditions against a set of ‘Master-stones’
Cut
Finally cut, which is the most important of all the 4C’s. Cut has the greatest opportunity to unlock the most potential out of the diamond; it is also the only factor that is influenced by man.
The standard round brilliant-cut diamond remains the most popular cut for diamond, when perfectly proportioned and cut with specific angles relative to one another this will show off the optimum optical effect of fire and brilliance. There are however, a myriad of other cuts that are equally prized for many different reasons. These are known as fancy cuts and they express the decorative and aesthetic potential of diamonds as well as the evolution of fashion and stone cutting over the years.
When it comes to the beauty of a diamond, CUT is the single most important factor. Cut is actually man’s contribution to the beauty of a diamond, for it is the cutter who releases the fire and brilliance of a stone. When we talk about cut, we are actually referring to its shape. Firstly its outline – is it round, square, or rectangular? And also what is it facet arrangement – that is the placement of the facets?
We can then describe the quality of the cut in different categories:
- Proportion – refers to the angles, proportions, and the relationship between the parts of a diamond.
- Symmetry – refers to the symmetrical appearance of the stone. E.g. the concentric positions of the table and culet for a round stone.
- Finish – the exactness of its shape and the arrangement of the facets. Also the quality of the polish.
All three of these elements together unlock a diamond’s optical potential.