At the origin of its sparkle
This is the only added value a human being can bring to rough stones, but what a value! The cut quality does not determine only the shape, but also the diamond brilliance. An expert knows how to perfect a stone's natural radiance with an ideally proportioned cut in order to play with the light, neither too hard nor too flat. This is the role of the stone cutter, the cutting specialist: mastering the light with precision when cutting the facets to reflect it even better. It is a strictly organized game of mirrors that makes the light flow out through the top and provides, therefore, an utmost brightness. The round brilliant remains the most used cut, with its 57 dazzling facets.
A diamond's weight, which is the only scientifically measurable criterion, is expressed as metric carats, a totally different unit of mass from the carats used to measure gold alloys. The word "carat" itself refers to the carob seeds, a tree from the Middle-East, whose seeds were used to measure little weights.
1 carat is equal to 0.20g or 200 milligrams, that is one fifth of a gram; the abbreviation of carat is "ct".
The carat is divisible into 100 points (hundredth of a carat), thus a 0.25-carat diamond has 25 hundredths of a carat.
There is a link between the weight and the diameter of a round-cut diamond. For example, whereas a 0.25-carat diamond measures 4.10mm diameter, a 0.5-carat diamond measures 5.20mm diameter.
Looking for perfection
All diamonds contain impurities, also called inclusions, that date from their formation. Let us not forget that diamonds are in fact pure carbon that were crystallized billions of years ago as a result of the pressure and the extremely high temperatures that prevailed at a depth of more than 200kms!
A diamond's degree of clarity depends at the same time on the number, the size, and the position of the inclusions in the stone. Some let the light shine through and, therefore, do not alter the sparkle of the stone. Gemologists reckon a diamond is pure or flawless in cases where no inclusions are observed under 10x magnification.
- FL (Flawless) : No inclusions or blemishes visible under 10x magnification.
- IF (Internally flawless) : No inclusions visible under 10x magnification, only small blemishes on the diamond surface.
- VVS1 and VVS2 (Very Very Slight Inclusions) : Tiny inclusions are extremely difficult to find, even under 10x magnification.
- VS1 and VS2 (Very Slight Inclusions) : Minor inclusions are difficult to find for a trained grader to see under 10x magnification.
- SI1 and SI2 (Slights Inclusions) : Inclusions are noticeable to a skilled grader under 10x magnification.
- I1 (Included #1): Inclusions are clearly visible under 10x magnification.
- I2 (Included #2): Inclusions and/or blemishes are obvious and easy to see without magnification.
- I3 (Included #3): Inclusions and blemishes are obvious to the unaided eye and they impact the brilliance of the diamond and its durability.
A magnificent rainbow
The rarest and most desired diamonds are colorless, identified by the letter "D" like diamond. The majority of the diamonds have a barely noticeable coloring, but sometimes more pronounced, listed with an alphabetic code, from D to Z, as the color intensity increases. From the letter "M", the term "colored diamonds" is used: pink, yellow, black, Champagne, Cognac, every color is represented. Blue, red, and green are the most exceptional colors.
Beyond the letter "Z", this is a different category of very significant value that experts call "fancies".