Grading white diamonds
The majority of diamonds that are mined are in a range of pale yellow or brown colour that is termed the normal colour range. Diamonds that are of intense yellow or brown, or any other colour are called fancy colour diamonds. Diamonds that are of the very highest purity are totally colourless, and appear a bright white. The degree to which diamonds exhibit body colour is one of the four value factors by which diamonds are assessed.
History of colour grading
Colour grading of diamonds was performed as a step of sorting rough diamonds for sale by the London Diamond Syndicate.
As the diamond trade developed, early diamond grades were introduced by various parties in the diamond trade. Without any co-operative development these early grading systems lacked standard nomenclature, and consistency. Some early grading scales were; I, II, III; A, AA, AAA; A, B, C. Numerous terms developed to describe diamonds of particular colours: golconda, river, jagers, cape, blue white, fine white, and gem blue, "brown".
Grading the normal colour range
Refers to a grading scale for diamonds in the normal colour range used by internationally recognized laboratories (GIA & IGI for example). The scale ranges from D which is totally colourless to Z which is a pale yellow or brown colour. Brown diamonds darker than K colour are usually described using their letter grade, and a descriptive phrase, for example M Faint Brown. Diamonds with more depth of colour than Z colour fall into the fancy colour diamond range.
Diamond colour is graded by comparing a sample stone to a masterstone set of diamonds. Each masterstone is known to exhibit the very least amount of body colour that a diamond in that colour grade may exhibit. A trained diamond grader compares a diamond of unknown grade against the series of masterstones, assessing where in the range of colour the diamond resides. This process occurs in a lighting box, fitted with daylight equivalent lamps, which are UV filtered. Accurate colour grading can only be performed with diamond unset, as the comparison with masterstones is done with diamond placed on its table facet and pavilion side facing upwards. When colour grading is done in the mounting, the grade is expressed as an estimated colour grade and commonly as a range of colour. Grading mounted diamonds involves holding the mounted diamonds table close to the table facet of the masterstone and visually comparing the diamond colour under the same colour conditions as unmounted diamond grading. The resulting grade is typically less accurate, and is therefore espressed as a range of colour. While a grading laboratory will possess a complete set of masterstones representing every colour grade, the independent grader working in a retail environment works with a smaller subset of masterstones that covers only the typical grade range of colour they expect to encounter while grading. A common subset of masterstones would consist of five diamonds in two grade increments, such as an E, G, I, K, and M. The intermediate grades are assessed by the graders judgement.
Diamond colour grading scales
Colour Grade D
D is the highest colour grade and is reserved for a truly colourless diamond. It is completely colourless to the naked eye and much sought after because it is so rare.
Colour Grade E
E grade diamonds are almost perfectly colourless, with only microscopic traces of colour which can only be identified by diamond experts.
Colour Grade F
F grade diamonds are almost totally colourless, with only minute hints of colour which can only be detected by experienced gemmologists.
Colour Grade G
G grade diamonds appear nearly colourless to non diamond experts. This grade offers excellent value for money.
Colour Grade H
H grade diamonds have a very slight tinge of colour which is only perceptible when evaluated next to a colourless diamond. They appear nearly colourless to non diamond professionals and offer an excellent investment.
Colour Grade I
I grade diamonds have very slight colour traces which are only evident when compared to a colourless diamond. To non diamond professionals they appear nearly colourless.
Colour Grade J
J grade diamonds have a very slight yellow tinge. They are an excellent choice for those on a budget who are not looking for a colourless diamond.
Colour Grade K
K grade diamonds have a very minor yellow hue. They are popular choice for the budget conscious.
Colour Grade L
L grade diamonds have a faintly tinted yellow colour. They are a good alternative for those not looking for a colourless diamond, and who are seeking excellent value for money.
Colour Grade M
M grade diamonds have a slightly noticeable yellow colour. They are often a good choice for those not looking for a colourless diamond.
Colour Grade N and Lower
N grade diamonds and lower colour grades have lightly tinged yellow colour. They are a good alternative for the budget conscious who prefer a diamond with some colour.