In ancient times, early gem traders discovered that carob seeds, with their uniform weight, were the perfect counterweights for their balance scales when weighing gemstones. Thus, the ‘carat’ became the standard unit of weight for all gemstones. In 1913, the United States adopted the metric carat which is equal to exactly 0.2 grams. Soon other countries followed suit and today that same metric carat is the global standard for measuring gemstones.
Carat weight is divided into 100 points, as in a 100-point diamond weighs 1 carat, yet the number of carats alone to not indicate a valuable gemstone.
The Four C’s combine to produce value:
- Carat – the weight of the gemstone
- Clarity – flawless or flawed
- Colour – brilliant white, pink, yellow, blue – each with their own rarity and unique value
- Cut – meticulous skills produce the cut that makes the most of each gemstone’s virtues
The finest diamonds are known for their fire, not their colour. This fire seems to explode from within the gem and the clearer the diamond, the brighter the fire and the greater the value. Most jewellery store diamonds will range from colourless to near-colourless, and along with the carat weight, will be rated by a colour-graded alpha scale.
Originally, colour grading systems were determined using alpha designators, such as A, B, C or multiples such as AAA. Even Roman and Arabic numerals were employed in some regions of the world. Ultimately, a standardised system was developed that could be used globally. This system begins with the letter “D” and grades the colour distinctions by comparison to gemstones of known colour as viewed under precise lighting conditions. Only highly trained gemmologists are capable of determining the subtle colour differences that can make a dramatic difference in a diamond’s value.
The extraordinary physical actions necessary to form diamonds within the earth can create unique birthmarks, known as inclusions (flaws within the gem) or blemishes (external flaws). These blemishes and inclusions are so common in diamonds that their absence is a rarity that dramatically alters the flawless gemstone’s value.
To ensure uniform grading of clarity, a system was developed that assigned clarity grades ranging from Flawless (FL) through to (I3) diamonds with obvious inclusions. The Diamond Grading System considers well-defined values: size, nature, position, colour and quantity of clarity characteristics visible under 10x magnification. This unified grading system allows jewellers around the globe to grade diamond clarity with an accuracy that translates equally to any nation in the world.
Skilled graders, using 10x magnification, use these clarity grades:
- Flawless (FL) - no inclusions or blemishes
- Internally Flawless (IF) - no inclusions, only blemishes
- Very, Very Slightly Included (VVS1 and VVS2) - inclusions are difficult to see
- Very Slightly Included (VS1 and VS2) - inclusions are clearly visible, but characterized as minor
- Slightly Included (SI1 and SI2) - inclusions are noticeable
- Included (I1, I2, and I3) - inclusions are obvious, may affect transparency and brilliance
The most beautiful diamond in the world, with substantial carat weight, absolutely colourless, and of flawless clarity, will have its accumulated value shattered if poorly cut.
A diamond’s value, in reference to how it is cut, depends upon precise proportions – often as tiny as 2 millimetres in diameter. Without this precision, the brilliance, fire and sparkle of a diamond will not be released and the diamond will lose much potential beauty. The proper cut for each particular diamond makes all the difference in the ultimate allure of the gem.
The elegant proportions used to produce a round brilliant cut diamond requires 57 or 58 facets, with each tiny facet exquisitely reflecting light in a way that creates breathtaking brilliance. The ratio of facets involves the related proportions of the table size (the large, flat facet on the top of the diamond), the crown angle and the pavilion depth. These delicate proportions dictate how the stone will interact with light, once cut.
The attributes that quantify the cut of any diamond are:
- Brilliance – the total light the diamond reflects
- Fire – the range of light dispersion into the colour spectrum
- Scintillation – the intensity of the flashes of light emitted when the diamond is moved
