Rough diamonds are sorted ( graded ) depending on their crystal shape , size and clarity before being sold to be cut and fashioned . In assessing the value of a cut diamond when buying or selling those in the jewellery trade will take four attributes into account . they are generally referred to as the 4 C’s . Color , cut , carat , clarity .
You may have heard a so called perfect diamond being referred to as a D flawless . this is the terminology used to describe a diamond with a color D ( the whitest and cleanest color ) and totally clear without any flaws or imperfections. Most diamonds however have a slight hint or tinge of color , usually yellow or brown . Without training and practice the very slight difference in in colorless diamonds are difficult to see. It is not until about grade M that the yellow tinge becomes more obvious. The bright colored diamonds ( including pink , yellow , blue , and green ) are called called fancy colored diamonds . they are described using different color schemes
Description / Color Grading
1 ) Colourless / D, E, F
2 ) Nearly Colorless / G , H, I , J
3 ) Faintly Yellow / K , L , M
4 ) Very Light Yellow / N , O , P , Q , R
5 ) Light Yellow / S , T , U , V , W , X , Y , Z ,
6) Fancy Colored Diamonds / Z +
Cut The shape of the cut and the make of the cut ( how exactly it has been cut ) are taken into account when assessing the cut of a diamond . The round brilliant cut is the most popular cut for diamond. The angles and dimensions of an ideal brilliant are worked out mathematically ( for example by diamond cutter marcel tolkowsky in 1919 ) to give the best possible shape and number of flat polished face ( facets ) to ensure that light which enters the gemstone is reflected back towards the eye of viewer . He developed the round brilliant cut by calculating eh ideal shape to return and scater light when a diamond is viewed from above. The modern round brilliant has 57 facets (polished faces ), counting 33 on the crown ( the top half ) . The girdle is the thin middle part. The function of the crown is to diffuse light into various colors and the pavilion’s functions to reflect light back through the top of the diamond. A well cut brilliant diamond will sparkle showing flashes of all the colors of the rainbow ( fire ) a badly cut one will appear dull and lack fire .
Carat The unit of weight used to measure diamonds is the carat ( 0.2 ) ( g = gramme ) . The name is thought to have been derived from the carob which is now used as a chocolate substitute .Each seed or bean of the carob is nearly identical in weight. Traditionally a one carat diamond was the same as the weight of one carob bean though it is now standardized as 0.2 g .In the far east rice was used as a comparison and one carob bean equaled four grains of rice. There are 100 points in a carat so half a carat diamond will weigh 50 points.
Clarity The clarity grading of a diamond is an asseddment of its inclusions and flaws .Internal flaws 9 inclusions are one type of flaw ) include for example cracks , air bubbles and the presence of other mineral within the diamond . Surface features include scratches chipped areas and pits which are also assessed . Surface flaws ( also called as blemishes ) may be caused as a result of cutting and polishing and care should be taken to check the girdle ( the widest part of the stone ) which separates the top ( crown ) from the bottom ( pavillon ) of the gemstone for marks . The cleaner the diamond the better its clarity grade and the more valuable it is .
Grading is carried out using a strong light and a X 10 magnifying lens . The grade and therefore the value and price are effected by inclusions but as no difference can be seen between a flawless diamond ( categorized as F ) and one with slight inclusions ( categorized as S1 ) without the x 10 magnification they look the same to the naked eye . It is only when the clarity reaches the grade ( impert I1 ) that the flaws can be seen .
Gem testing laboratories can prepare a plot ( line drawing or sketch) of a diamond’s inclusion and include this on a diamond grading certificate . In the same way that no two people will have same fingerprint no two diamonds will have the same clarity plot .
Clarity Grading / Description
1. F / Flawless . No internal or external flaws . Extremely rare .
2. IF / Internally flawless . No Internal flaws but some surface flaws . Very rare
3. VVS1 – VVS2 / Very very slightly included ( two grades , VVS1 is the least included) .Minute inclusions very difficult to detect under X 10 magnification by trained gemologist
4. VS1 – VS2 / Very slightly included ( two grades ) . Minute inclusions seen only with difficulty under x 10 magnification
5. SI1- SI2 / Slightly included ( two grades ) .Minute inclsuionsmore easily detected in X 10 magnification .
6.I1 – I2- I3 / Included ( three grades) .Inclusions visible under X 10 magnification .Inclusions also visible to naked eye .