The 4 c's of Diamonds - Part 2 of 5 - Colour

Diamond Colour Grading & Rarity

Colour or absence of it, is a defining factor in diamond evaluation and one of the 4Cs GIA (Gemological Institute of America) included in each official diamond report. The GIA colour grading runs alphabetically from colourless ‘D’ diamonds (the purest) to ‘Z’ ones that contain the most chemical impurities, especially nitrogen atoms whose arrangement inside the stone can cause from subtle to visible yellow/brown tint. People have been grading diamond colour since the early 1700s, yet GIA’s most reliable system was first presented in the 1950s. Once attested by the experts, colour is taken as an indication of rarity, not of quality. The way you appreciate it, is completely subjective. Icier or warmer shades match (or do not match) certain metal settings in jewellery. Yellow gold for example can reflect colour onto high colour grade diamonds and in these cases platinum or white gold settings are preferable. Even yellow gold rings are often made with Platinum settings to prevent the Diamond from drawing colour for the metal.

The Process

A member of the public will be able to spot the colour in a Diamond at around a ‘J’ or ‘K’ colour (the 7th & 8th colours) & lower. The untrained naked eye though, often lacks the ability to trace small concentrations of ‘tint’. This means that any Diamond weighing 0.20ct or over should be sold with a laboratory report for proof of an honest grading. When a laboratory like the GIA tests a Diamond each stone is unset and placed upside down (meaning resting on its ‘face’) in a white lighting box emulating daylight so that the tester is looking at its body or ‘pavilion’ and not get distracted by the light (brilliance) reflected from the table facet to their eyes. A master set of diamonds (usually E, G, I, K, and M) that contain the least of colour for their respective grades is used as a point of comparison with the sample stone. The trained grader will assess its colour using their expert judgment after side-by-side comparison. It’s all about experience & cross-checking multiple times. They are figuring out where in the colour range each sample stone stands.


Other considerations

When shopping for diamonds think of the ring or other piece of jewellery they are part of. Round brilliant diamonds show off the least of imperfections and colour differences so you can get lower in colour or clarity grade without a very visible flaw. On the other hand, stepped cuts with larger facets are clearer indicators of the stone’s hue. Add to the strictly technical 4Cs a fifth criterion which is the overall beauty and desirability of each diamond. Make sure that you see it in daylight to realize how it performs in natural conditions. Brilliance or ‘fire’ in a diamond is tested via the Weighted Light Return (WLR) method, which explains what you actually see in natural light. For example, among two D (colourless) diamonds you might realize that one is dazzling more due to better internal structure. An F diamond might look better than a D because internally the crystals might allow the least of light leakage and secure the most of reflections through the table facet. For similar reasons, one lower-grade stone might have prettier colour contrasts which are again mostly visible via magnification yet still add up to very visible brilliance. We are always available to advise you on each jewellery piece and stone guiding you through a smart decision based on your budget. Click here to take a look at some of our engagement rings.


Fancy Diamonds

It might exceed the scope of our topic, which is diamonds in the normal colour range (D to Z), yet looking briefly into what is classified beyond the Z letter will give you a better understanding. Most diamonds mined in the world run from colourless to pale yellow or brown. If yellow is too intense, nitrogen impurities are dispersed in a very special way within the crystal. Diamonds of bold yellow or other intense colours are graded beyond Z and are called fancy diamonds. They are found globally in very small percentages, with red and blue being the rarest. They were created due to accidental structural defects and chemical inclusions as the stones face high pressure and heat during crystallization on their way up through earth’s layers. When fancy diamonds are evaluated, the largest amount of colour the highest the price, while for D to F diamonds, the least of colour the highest the price tag. Still, as a customer, always keep in mind that you are as unique as the hue of your preferred diamond! 

You can find out more about diamond grading by clicking here.

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