Coloured Diamonds

Diamonds are seldom white. In fact so called 'white' diamonds are graded from colourless at D to pale yellow at Z. The point at which the colour become detectable by the naked, untrained eye is around J. (See the Diamonds page for more details of diamond grading.)

Natural diamonds are also found in almost all colours from yellow to steel grey to bright blues and oranges. The intense colours are very rare and attract high prices, with red being the rarest and, therefore, most expensive. These colour variations are due to the presence of natural impurities in the material or imperfections in the crystal lattice that cause the diamond to pass light differently. These stones, with a colour beyond 'Z' are known in the trade as 'Fancy diamonds' and the best ones are amongst the most expensive stones you can buy.

I had a client once who announced that she wanted a pink diamond in her engagement ring 'like Jennifer Lopez' She had £500 to spend and I had to point out that a moderately sized pink diamond was going to cost her more than £40,000. She settled for an off-white stone in the end!

White or off-white diamonds can also be coloured synthetically after they have been cut and polished. The stones in this ring are of this kind. To achieve the colour change the diamonds are bombarded with alpha particle radiation which knocks carbon atoms out of their place in the crystal lattice and thus creates areas of the material that refract light differently. The colour produced is normally a deep green, black or blue and this is further altered by heating in order to mobilise the carbon again and repair some of the defects created during the radiation phase. This allows a close control over the colour of the final stone, resulting in the shades of red, pink and blue that are most commonly used within the jewellery trade.

Please note that although this process is known as irradiation, the stones produced are not radioactive and won't give you cancer!