1) Cut – This is determined by human intervention. The other factors are all born by nature. This is where the highly skilled diamond cutter will evaluate the best cut for the stone. By assessing the diamond in the rough, an experienced cutter will bring out the best in the stone. He will choose a cut and shape that will show off its natural beauty. The most popular cut is the round brilliant, a classic, chic cut that has 57 facets on every stone. The number of facets and the angles between them are worked out mathematically so that the facets act as mirrors that allow the maximum amount of light reflect and refract throughout the stone. There is a difference between “cut” and “shape”. They can be confused, but “shape” is quite literally the outline of the stone; round, square, oval etc. The cut is how the stone is fashioned/faceted. There are many different cuts; Brilliant, Asscher, Baguette, Emerald and Cushion are some of the more popular cuts. When a diamond has been cut to perfect proportions, its brilliance, scintillation, radiance and inner fire will be set alight. A badly cut stone will have little reflection and appear dark.
2) Colour – diamonds are very individual and very unique. Each stone has its own inner fire. They are graded by “Colour” by the “GIA” who developed an international scale of grading the colours of diamonds, ranging from “D”, which is colourless – pure white, all the way down the scale to “Z” which is quite yellow. “D” colour diamonds are very rare and highly desirable. “G, H and I” are very good stones. You can just make out a slight yellowish tint from about grade “K/L” onwards. Any colour beyond “Z” becomes a “Fancy” colour. These can come in any other colour, and pale champagnes should not be muddled with a poor colour white “T+” graded stone. “A’s B’s, and C’s” are not used, quite possibly reserved for if and/or when a better stone than a “D” makes an appearance……Some other organizations refer to the colour of stones by different terms, for example; CIBJO refer to a “D” stone as “Exceptional White +”, and “E” stone as “Exceptional White”, an “F” stone as “Rare White +”, “G” = “Rare White”, “H” = “White”, “I/J” = “Slightly Tinted White”, “L/K” = “Tinted White” and “Tinted Colour” would rank about “M+”. The GIA scale is probably the most commonly recognized and fairly easy to grasp.
3) Clarity – degrees of flawlessness. Graded using a 10x magnification loupe, a diamonds’ blemishes are taken into account whether inside or outside the stone. Most stones will have natural inclusions, (Nature’s Hallmarks). It is rare to find a flawless stone. The inclusions appear as little black specs, cracks and fissures. They are natural occurrences created whilst the stone was forming. Their presence in a Diamond will determine their clarity. Most of the smaller inclusions are not visible with the naked eye. Once again, the GIA have developed a scale for measuring the inclusions. They are graded as “IF” for “Internally Flawless” or “Loupe Clean” according to CIBJO, “V V S 1” and “V V S 2” for “Very, Very Slightly included, “V S” for “Very Slightly” included, “SI” for “Slightly Included”, and “I 1/2/3” for “Imperfections”, or “Pique” which are visible to the naked eye.
4) Carat – a “carat” weighs 0.2 grams. All stones are weighed before setting for an accurate measurement. A stone is measured in points where one carat equals 100 points. If the total weight of the stone is 50 points then the stone is ½ a carat, or can be shown as 0.50. To weigh a stone in a ring, perhaps for valuation purposes, it must be removed from the setting for an accurate measurement. The weight can also be “Estimated” if measured, there are complex calculations that can be done to do this, but a single carat may be in the region of 6.5mm in diameter. Carat does not necessarily denote the size of the stone, a shallow 50 pointer will appear larger than a deeper stone as it has a larger visible surface area.
5). The hidden 5th C is the Certification. If a stone is over ½ a carat, it may well have a certificate displaying all the weights and measurement of the stone, including the colour, clarity, cut and carat weight. There can be much other information to be gleaned from a certificate, too. The GIA laser inscribe diamonds with a registration number, this in inscribed on the girdle of the stone and appears on the certificate. There will also be information about the clarity characteristics, the finish, the polish, the fluorescence, symmetry and actual stone proportions.