Natural or”¦

Given the demand for fancy colour diamonds and the high prices they command, knowing the origin of their colour is critical. As for all gemstones, honest disclosure is mandatory; natural fancy colour diamonds (i.e. other than brown and light yellow) are very rare, and their value reflects that. If you are purchasing a significant stone, it is vital it carry a certificate of natural origin from a reputable laboratory to guarantee the source of the colour. As with the current situation involving undisclosed white lab-grown diamonds, there have been parcels of melee and even larger fancies ‘salted’ with either treated or man-made stones. It is a case of buyer beware.

Man has manipulated diamonds for centuries to change their colour. Early methods (fortunately not as often encountered today) included painting transparent colour on the girdle or, more effectively, on the stone’s culet. These ‘enhancements’ are fairly easy to discover, though if a stone is in a relatively closed-back setting, it can be more difficult. Any serious cleaning with an ultrasonic and steam removes the coatings.

Irradiation of natural diamonds to change their colour has been around for many years. Initially, this was mainly used to change off-colour brown or yellow stones to intense turquoise blue or deep yellow. However, in more recent years, a wider range of shades can be achieved using other methods. Varied combinations of high-pressure/high-temperature (HPHT) treatments have more recently allowed the production of diamonds in various intensities of yellow, pink, purple, green, and also more ‘natural’ shades of blue. Lab-created diamonds have become quite widely available in the last few years and some of the fancy colours are very attractive.