Colour

Colour is one of the four factors (4C’s) in grading a diamond, both lab grown and mined. Diamond colour evaluation is actually based on the absence of colour, a chemically pure and structurally perfect diamond has no hue. Many of the colour distinctions are invisible to the untrained eye which is why the Gemmological Institute of America and other labs use the D-to-Z diamond colour-grading system. With this they compare the diamond with established master stones under controlled lighting conditions. These distinctions make a huge difference in diamond quality and price so it’s important to get an expert opinion.

It’s actually incredibly rare to find a diamond that completely lacks colour. Diamonds with a poor colour grade can appear yellow, instead of the desired brilliant white but they can also be found in any naturally occurring colour, including pink, yellow and green. D is the best grading you can get as it lacks all colour.

Lab grown diamonds can share the same colour flaws as mined, as the mining process is replicated in a laboratory the same way. There are actually a wide range of colours that depend on the lab’s level of technology. Some have the knowledge and tech to create colourless grades, others do not. However, the technology is constantly developing, unlike the unpredictable mining process. Lab grown diamonds are graded in exactly the same way as mined diamonds.

HOW IS COLOUR GRADED?

The first official grading (or rating as it is less commonly called) of Diamonds was by the London Diamond Syndicate, in order to sort through rough Diamonds for sale. Up until the 1940s there were many different colour systems used by diamond traders, for example the first three letters of the alphabet, numbers and Roman numerals. These often led to confusion, inconsistencies and inaccuracies. 

In order to avoid confusion and create an accurate international system, the Gemmological Institute of America (GIA) introduced a fresh colour scale, which is now the accepted industry standard for grading diamonds.

WHAT ARE ‘FANCY’ COLOURED DIAMONDS?

Fancy coloured diamonds go off the typical colour scale as they have distinct and opulent hues that come in every colour of the spectrum, including blue, green, pink, and red. Therefore, the above guide does not apply to these stones.

Coloured diamonds are highly prized and rare (one in every 10,000 mined diamonds (0.0001%) possesses natural colour). Unlike colourless diamonds which are valued for their lack of colour, fancy diamonds are valued for their intensity.

The key point to note is that fancy diamonds are formed through a glitch in the creation process; colourless diamonds will possess only carbon, impurities are what gives it a coloured tinge. Lab grown and mined coloured diamonds are created in exactly the same way, the scientist simply just replicates the process found in nature and so colourless diamonds can be created on purpose in a lab.

An advantage of creating coloured diamonds in a lab is that it’s much easier for scientists to experiment in a controlled setting. Whilst the science behind creating ‘fancy’ lab diamonds is kept protected by the labs, in a ‘natural diamond’, they are created by combining carbon with other chemicals. An educated assumption is that this process is mirrored in the lab. For example;

• Yellow, Brown, and Orange Diamonds: nitrogen and carbon

• Blue Diamonds: boron and carbon

• Green diamonds: gamma radiation

• Pink and Red diamonds: higher pressure, distorting the diamond’s lattice

Are diamonds graded Z fancy-coloured?

No. They fall outside of the typical grading system. Whilst the FTC doesn't actually provide any guidelines for the use of the term “fancy-colour”, it is agreed within the industry about what colour range is customary for fancy-colour diamonds. They are usually yellow or brown and have more colour than a Z master stone, or they exhibit another hue.