Diamond Four Cs
How to buy a diamond: round, oval , pear, heart, marquise, princess, emerald, radiant, asscher, cushion, trilliant
There are four factors (Four Cs) that contribute most to the value and look of a diamond. These are:
Understanding the Four C's is the first step in your journey to buying the perfect diamond so each one is explained below.
CUT refers to the proportions, symmetry and finish of a polished diamond. To get from the raw diamond to the cut gemstone requires the skilled hand of a master cutter. The better the CUT proportions, the better the diamond handles light to create sparkle. Therefore CUT is the single most important factor affecting a diamond's sparkle, brilliance and visual fire as illustrated with the following diagrams for a round brilliant-cut stone:
A well-cut diamond reflects maximum light and so sparkles the best. Shallow-cut and deep-cut diamonds let the light escape at the sides or bottom.
Deep Cut Diamond
Shallow Cut Diamond
Well Cut Diamond
The sad fact is, 75% of all rounds and 88% of all other shapes on the market are poorly proportioned to retain carat weight rather to maximise sparkle.
A well-cut diamond loses more of the rough diamond than deep or shallow cuts as illustrated below.
Natural rough diamond
2 Diamonds cut with well-cut proportions. For example this may yield a larger diamond of 1 carat and a smaller diamond of 0.5 carat
2 Diamonds cut to retain maximum carat weight and not ideal sparkle proportions. For example, this may yield two diamonds of around one carat.
There are three components to diamond brilliance: white light return, dispersion and scintillation. White light return is the percentage of light observed coming out of a diamond. Dispersion, sometimes called fire, is the break-up of white light into the rainbow of spectral colours. Scintillation is the sparkling aspect of a diamond when it is moved. All of these factors are finely related and need to be balanced carefully by the cutter as maximising any one will decrease the other aspects.
The CUT proportions of a diamond affects its price, sometimes by as much as 40%! HRD, GIA and IGI certificates give grades for cut proportions for round brilliant diamonds. The most research has been done so far on what proportions contribute to the sparkle of the round shape - due the the 360 degree symmetry of the round shape, it is easier to define a set of parameters for proportions.
The term fancy shape diamond is used to describe all other diamond shapes that are not round brilliant e.g. princess, pear, emerald cut, radiant, cushion, asscher, oval, heart, marquise...etc.
Unlike round brilliant diamonds, there are no defined range of proportions which can be used to predict in advance whether a fancy shape diamond (e.g. princess, pear, emerald cut, radiant, cushion, asscher, oval, heart, marquise...etc) is well-cut. Hence, the HRD, GIA and IGI do not give any cut proportion grades for fancy shape diamonds. Hence, the best way to judge a fancy shape diamond and whether its well-cut is to see it!
CUT is confusingly also used to refer to diamondSHAPE.
There are a number of shapes which diamonds traditionally take, depending on the original nature of the rough, uncut stone.
The most popular shape for a diamond is the round brilliant diamond which is aptly named as when well-cut, the round diamond reflects the maximum light and sparkles more than any other shape. They are also slightly more expensive than any other shape because 50% of the rough diamond is lost when cutting a round shape and less is lost when cutting any other shape.
After the round brilliant diamond, princess cut diamonds (a square shape) are the most popular. For example, out of 100 diamonds produced: 80-85% will be round brilliants, 5-10% will be princess cut diamonds and the remainder will be spread across all the other shapes possible e.g. pear, emerald cut, cushion, asscher, radiant, heart, oval, marquise, trilliant...etc
Round Brilliant
Oval
Pear
Emerald
Marquise
Heart
Radiant
Princess
Asscher
Cushion
Trillion
Diamond colour is a key parameter in determining its value as well as its beauty
From the faintest yellow or brown to the very rare pinks, blues, greens and other colours (known as "fancies" in the trade) it is still no colour at all that takes the cake when it comes to diamonds. A completely colourless diamond allows white light to pass through it effortlessly - dispersing it again as rainbows of colour.
The diamond colour scale starts from D (The best blue White) to Z (for dark coloured diamonds).
Of all the diamonds that are suitable for selling in jewellery, only the top 8% have the colours D to G i.e. these are relatively rare. For white/colourless diamonds, the top colours: D (the Best Blue white), E (exceptional white), F (Very very white),G (rare white), H (white) and I (slightly offwhite) are all considered "white" when set in a ring and are hard to tell apart to the untrained eye: e.g. an E is hard to tell from a D, an F is hard to tell from an E, though the difference between say a D and an H may be more discernible when the diamonds are compared loose.
Professional grading labs judge colour from the side of the diamond not from the top.
Hence its impossible for even an expert eye to tell the difference between adjacent colours e.g. D, E and F for instance when viewed the top.
Colours from "K" show a slight "yellowing" and this effect increases as the diamond size increases.
The majority of diamonds are born with miniscule "birthmarks" known as inclusions. The smaller and fewer the inclusions, the more light can pass through the diamond, contributing significantly to its rare beauty. More than any other gemstone, diamonds are capable of producing the maximum amount of brilliance. Thus a diamond which is free of inclusions and surface blemishes is more rare and, by definition, more valuable.
A diamond's clarity can be affected by two types of flaws:
- External flaws: these are any of the impurities that are on the surface of the diamond. External flaws are the result of wear and tear on the diamond or from damage caused during cutting.
- Internal flaws: These are any of the many impurities that reside solely in the interior of the diamond. There are many kinds of internal flaws. A few important ones that you should familiarize yourself with are:
- Black or dark spots: carbon or other dark spots.
- Clouds: Clouds, are microscopic inclusions that lower transparency.
- Fracture (feather) - the majority of imperfections in diamonds are the result of breakage in the diamond chemical structure.
Clarity Grading:
The most common instrument used for Clarity Grading is the hand held loupe or microscope (based on 10-power magnification). This means, for all intents and purposes, any imperfection that cannot be detected with a x10 magnification does not “exist” while grading a diamond.
I.F Internally flawless: Free From internal blemishes visible under 10x magnification (small external details tolerated).
V.V.S 1 Very very slightly included: Inclusions and/or external blemishes very very difficult to locate under 10x magnification. 
V.V.S 2 Very very slightly included: Inclusions and/or external blemishes very difficult to locate under 10x magnification.
V.S 1 Very Slightly included: Inclusions and external blemishes difficult to locate under 10x magnification.
V.S 2 Very Slightly included: Inclusions and external blemishes rather difficult to locate under 10x magnification.
S.I 1 Slightly included: Inclusions and external blemishes rather easy to locate under 10x magnification.
S.I 2 Slightly included: Inclusions and external blemishes easy to locate under 10x magnification.
P.1 - 1.1 Imperfect: Inclusions and external blemishes very easy to locate under 10x magnification.
P.2 - 1.2 Imperfect: Inclusions and external blemishes easy to locate with naked eye.
P.3 - 1.3 Imperfect: Heavy inclusions located with naked eye.
Diamonds were first discovered in India around 500 B.C. The first unit of weight used for diamond was the carob seed; the weight of a seed from the seed pod of the carob or locust tree was equivalent to a 1.00 ct. diamond.
The weight of a diamond is measured in carats - one carat is 0.2 gramme. This is the easiest factor to determine. However, weight is related to but is NOT the same as size! Two diamonds of the same shape cut from the same rough (with equal carat weight, colour and clarity) can be different size depending on how well they have been proportioned. The better cut diamond will appear bigger than a less well-cut diamond! Also as diamond prices go up exponentially with carat weight, doubling the carat weight from say 1 carat to 2 carats more than doubles the price, but the visible size of the table (the largest surface at the top of the diamond) goes up by only by ca. 30%. As about 50% of the rough diamond is lost when cutting, the larger the diamond the rarer it is in nature hence the price increases most steeply with carat. Approximately 250 tons of ore must be mined and processed in order to produce a single, one-carat, polished, gem-quality diamond.
Overall, for any given carat – the price also varies considerably with colour and clarity. For example for a loose 1 carat round brilliant diamond the trade price for a D (the best blue white colour) Internally Flawless (loupe-clean clarity) is more than FOUR times the price of a 1 carat H (white colour) VS2 (eyeclean++ clarity) diamond! This difference reflects rarity rather than visible differences: less than 0.003% of all 1 carat diamonds have the combination D colour and IF clarity! Only 8% of the jewellery quality diamonds even have the combination of G VS2 or better!
Carat
|
0.40 |
0.50 |
0.70 |
0.9 |
1.00 |
1.25 |
1.50 |
1.75 |
2.00 |
2.50 |
Diameter mm |
4.8 |
5.2 |
5.8 |
6.3 |
6.5 |
6.9 |
7.4 |
7.8 |
8.2 |
8.8 |
Height Mm |
3.0 |
3.1 |
3.5 |
3.8 |
3.9 |
4.3 |
4.5 |
4.7 |
4.9 |
5.3 |
Trade Price |
0.15 times X |
0.24 times X |
0.44 times X |
0.7 times X |
X |
1.4 times X |
1.92 times X |
2.5 times X |
3.5 times X |
4.75 times X |
To find our more or arrange a visit to see us, contact Dr Indira Marchant on +44 208 868 5210 or email info@bestdiamonds.co.uk
