Understanding the 4 ‘C’s is crucial before making any Diamond purchase. Cut, Colour, Clarity and Carat have an enormous impact on the price of Diamonds. By having knowledge of each of these factors you are able to make an informed choice of the many thousands of diamonds being offered for sale in the market place.
The ‘Cut’ of a diamond is considered by many to be the most important of the 4’c’s. It is the overall cut of a diamond that is the major contributing factor determining brilliance and scintillation.Diamonds are cut in a variety of shapes however the most popular shapes today are the Round Brilliant cut and the Princess cut. On the diagram below are the accepted range of percentages and angles for the ‘Perfect’ Ideal Round Diamond.
For a diamond to have perfect brilliance and scintillation all shapes have certain proportion standards to meet which result in high weight loss of the rough crystal. Sometimes the diamond cutters compromise and accept lesser proportions and symmetry in order to avoid inclusions and/or to preserve carat weight.
The diagram below clearly illustrates how light travelling into the stone from the table is lost through the sides if the diamond has been cut either too deep or too shallow. Only if the diamond has been cut perfectly that light will be returned back throught the table giving perfect brilliance and scintillation.
HEARTS & ARROWS
Hearts and Arrows diamonds are round brilliants with special patterns visible under specific lighting conditions. They consist of eight hearts when viewed from the pavilion side and eight arrows when viewed from the crown side. Kinsaku Yamashita designed in 1988 an appropriate viewer (below) which creates the typical images illustrated on the right. The H&A pattern is very sensitive to symmetrical imperfections. Because of the high degree of symmetry and the limited proportion sets for which the patterns are visible a premium price is paid for H&A diamonds. The appearance of the pattern is a strong indicator of a top quality cut. Each of the major Internationally recognised laboratories such as GIA, AGS, HRD and IGI have their own set of grading criteria which are all slightly different so there are small tolerances between the grading houses on what the dimensions create ‘ideal cut diamonds’.
The pattern of eight hearts should be the same size,all clearly visible,sufficiently bright showing no colour with the overall pattern being uniform.
The shoulders of the hearts should be flattened.Pointed shoulders are a result of table size being greater than 60%.
The hearts should have symmetrical points.Asymmetrical points are a result of an offset between the left and right side of the hearts.
There should be a space between the heart and the v underneath the point of the heart, with all eight v’s being well balanced.
The pattern of eight arrows should be the same size,all clearly visible, sufficiently bright showing no colour with the overall pattern being uniform.
The star shaped pattern in the centre ,formed at the base of the arrows shafts should not be too large, a consequence of this being arrows which are too short.It should also resemble a star shape and not have white areas that surround the shafts of the arrows, this will affect the star shape in the centre.
Colour being one of the 4 c’s plays an important factor in choosing a diamond.If choosing a white diamond then the less colour is more desirable.GIA use the alphabet to catagorise colour.The absolute finest colourless stone is graded a D, descending through each letter of the alphabet to Z being a diamond that is tinted yellow in colour.
Below is a table with the most prominent Diamond Colour grading scales used today.
The Gemological Institute of America, GIA, using alphabetical letter grades and description.
The American Gem Society, AGS, using numerical number grades and electronic colorimeter scale.
The World Jewellery Confederation, CIBJO, using a word and number description.
|D||Colourless||0||0 – 0.49||Exceptional White +|
|E||0.5||0.5 – 0.99||Exceptional White|
|F||1||1 – 1.49||Rare White +|
|G||Near Colourless||1.5||1.5 – 1.99||Rare White|
|H||2||2 – 2.49||White|
|I||2.5||2.5 – 2.99||Slightly Tinted White|
|J||3||3 – 3.49|
|K||Faint Yellow||3.5||3.5 – 3.99||Tinted White|
|L||4||4 – 4.49|
|M||4.5||4.5 – 4.99||Tinted Colour 1|
|N||Very Light Yellow||5||5 – 5.49||Tinted Colour 2|
|O||5.5||5.5 – 5.99|
|P||6||6 – 6.49|
|Q||6.5||6.5 – 6.99|
|R||7||7 – 7.49|
|S||Light Yellow||7.5||7.5 – 7.99||Tinted Colour 3|
|T||8||8 – 8.49|
|U||8.5||8.5 – 8.99|
|V||9||9 – 9.49|
|W||9.5||9.5 – 9.99|
Clarity being one of the 4 c’s plays an important factor in choosing a diamond. Diamonds are graded on a scale from FL (flawless) through to I3 (included to 3rd degree). There are many types of inclusions found in diamonds and all are given different names, feathers,clouds,pinpoints and so on.
Below is a table with the most prominent Diamond Clarity grading scales used today.
The Gemological Institute of America, GIA
The American Gem Society, AGS
The World Jewellery Confederation, CIBJO
|VVS1Very Very Slightly Included 1||VVS1|
|VVS2Very Very Slightly Included 2||2||VVS2|
|VS1Very Slightly Included 1||3||VS1|
|VS2Very Slightly Included 2||4||VS2|
|SI1Slightly Included 1||5||SI1|
|SI2Slightly Included 2||6||SI2|
|I1Included 1||7-8||P1Pique 1|
|I2Included 2||8-9||P2Pique 2|
|I3Included 3||9-10||P3Pique 3|
The carat is a unit of measurement commonly used for weighing gemstones and pearls. 1 carat is equal to 200mg. The carat can be divided into 10 points of 2 mg each. Quite simply, the more carats, the larger the diamond.