How to Judge Colour Diamonds

Colour diamonds refer to stones that commonly host a colour as a result of chemical reactions during the formation or extraction process – scientifically speaking. Diamonds - regardless of the presence of colour - are made of carbon, however it is through the process of commuting 300 miles from the floor of the earth to the surface do diamonds alter in colour. The basic four colours include pink, yellow, green and blue; other colours such as brown, orange and red are secondary combinations. As De Beers’ diamond expert puts it, “Pink, yellow, green and blue diamonds are created in completely different ways, whereas brown, orange and red is a combination of alterations. Mother Nature doesn’t only cook it one way”. To better understand how the colour diamonds are created, we pick Coxon’s brains for expert insight:
 

Blue diamonds: This is the presence of boron atoms and a blue diamond is extremely rare. Coxon reminds us of the round brilliant five-carat diamond that went into auction in Hong Kong: the reserve price was five times the price of a grade D diamond of the same size, but later it was bought by a buyer for two times the reserve price.

Yellow diamonds: The yellow in the diamond is the result of nitrogen atoms in the stone and it is harder to find a nitrogen-free diamond than one with nitrogen. However, if it is heavily saturated with yellow, then it becomes fancy yellow and is acknowledged as a colour diamond. Orange diamonds is a combination of nitrogen and a distortion of the atomic lattice.

Pink diamonds: The pink in a diamond is a result of a distortion of the atomic lattice, which occurs when a diamond is put under high pressure and high temperature. When the pressure is abnormally high, the diamonds come out dark brown or pink, predominantly brown. Take for example, the diamonds from Argyle in Australia are 95 percent brown and five percent pink. Red diamonds on the other hand is a continuation of the process.

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Green diamonds: Natural radiation gives diamonds a green skin and prolonged exposure will make the stone itself green. A natural green diamond of half a carat will go for 10 times the price of a colourless diamond.

Unlike colourless diamonds which are commonly judged by the four C’s and Coxon’s own De Beers criteria that includes fire, life and brilliance, a coloured diamond is recommended to be judged by its saturation, tone and hue. To learn more about this, watch our video interview above with Coxon, who gives a masterclass on judging colour diamonds.

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