GIA Gemological Institute of America pioneered the universal colour grading system for diamonds in the early 1940’s to overcome all the confusing colour grading systems in use. The GIA colour grading classification starts from D, the finest colour grade (colourless), and continues through the alphabet to Z becoming progressively more tinted to yellow. A set of master comparison stones calibrated to the exact colour of every colour grade is the most reliable method of grading diamonds for colour. This allows for the accurate colour grading of the diamond.
Diamond Colour Grading
Grading polished diamonds for colour means determining the amount that the diamond’s “body colour” deviates from the whitest possible (water like colourless) colour. This concept should not be confused with the sparkle, brilliance, or scintillation of the diamond.
Because diamonds have a high brilliance and dispersion of light, the colour grade cannot be accurately determined by looking at the stone from the top (face up) position. It is best to observe colour by examining the stone through the side of the pavilion (bottom of the stone) with the diamond upside down in a white grading trough.
Diamonds are found in a variety of colours. The rarest diamonds are ones that have a colourless grading or diamonds with fancy colours such as greens, blues, reds and pinks.
Diamonds that are colour graded in the D-F range are the rarest and consequently most valuable. In reality, diamonds in the G-J range have such a small amount of colour that the untrained eye can not see it and as such offer great value.
Diamonds that occur by rare accidents of nature in shades of pink, blue, green, amber, or even red are known as fancy coloured diamonds and are evaluated by a different set of colour grading standards. These standards take into consideration various factors such as hue and saturation. Fancy coloured diamonds are expensive because of their extreme rarity and colour.
Diamond colour has a significant impact on its value. The colour scale ranges from D to Z, from colourless to light yellow, respectively. The further from colourless that a diamond is grade, the less rare and therefore less valuable it becomes. When buying a diamond, take into consideration that it is often very difficult to detect the difference between a colourless diamond (D-F) and a near colourless diamond (G-J), especially when it is mounted in jewellery.
Diamonds with a K-Z colour grade usually have yellow shading that can be detected by the naked eye. A well cut diamond with good proportions in a lower colour grade will still release the brilliance and fire of a diamond in a higher colour grade, dispersing light in such a way that diamonds with a lower colour grade are still extremely attractive and look beautiful in jewellery. The colour of a diamond is not the only deciding factor to determine the value, there is a combination of qualities including cut, clarity, carat weight and the shape of the diamond that all help to determine and influence the value of the diamond.
Diamonds with a higher colour grade, appear whiter. The whiter the diamond, more light is able to pass through it, making it sparkle and shine. Diamonds with a colour grade of J and higher are near-colourless or colourless, and are recommend best value, since their colour is undetectable to the untrained and unaided eye.
The grades D, E, F are exceptionally fine white diamonds being the only grades referred to as colourless. E colour diamonds are extremely close to D colour diamonds, however the colour variance can only be detected in a controlled diamond grading environment. The variance in price per carat between a D and E colour diamond is significant at the wholesale level reflecting the rarity of these diamonds in the market.
Near Colourless Diamonds
Faint Yellow Diamonds
Very Light Yellow Diamonds
Even though the most valuable diamond is D colour, a diamond which grades G through J will appear nearly colourless. Sometimes a jeweller will speak of how diamonds “face up” to the eye, referring to the fact that diamonds are graded for colour from bottom of the stone and therefore give the illusion of less body colour from the top because facets on the diamond disperse spectral colors to the eye.
Fluorescence is not directly related to a diamond’s colour. This is a separate characteristic and it refers to the diamond’s ability to fluoresce under ultraviolet (UV) light. Our sun emits some UV light, but it is usually not great enough to detect fluorescence. The most common source of UV is a black light. When exposed to UV light, many diamonds will give off a distinctive glowing blue coloration. Although fluorescence may be displayed in various colours, blue is the most common in diamonds. The fluorescence of a diamond is defined by its intensity as either None, Faint, Medium, Strong, or Very Strong. Although fluorescence is a characteristic that can be measured, it is seldom an issue when selecting a diamond.
The effect of fluorescence depends on a combination between the colour of the stone and the strength of the fluorescence. Faint fluorescence has very little effect on a stone of any colour. Medium blue fluorescence and strong blue fluorescence can have a positive effect on stones of lower colour (J or lower). The fluorescence actually has the effect of making the stone look closer to near colourless. On stones of high colour (D-G), strong or medium blue fluorescence may cause the stone look milky instead of colourless or near colourless.
Knowing the subtle differences between the sub-groups in the diamond colour grading classification system and the major impact these changes have on the wholesale price, it is highly recommended that the diamond comes with a Diamond Grading Report from an independently recognized diamond grading laboratory. This Diamond Certificate is a way to ensure the quality of the diamond and it will give you a better understanding about the specifications of the diamond before making any purchase.