Selling fancy coloured diamonds

The diamond market is sluggish and prices are falling, yet fancy coloured diamonds are among the hottest gems on the market today. They are continually setting auction records, often in the tens of millions of dollars. Fancy coloured diamonds come in every colour of the rainbow and command steep prices. Fortunately, not all coloured diamonds are priced in the stratosphere.  There are a few things you should know if you are interested in stocking fancy coloured diamonds.


Fancy coloured diamonds


Colour is King

You are familiar with the 4Cs of diamonds. With colourless diamonds, the 4Cs have an equal effect on price. Although all the characteristics will play a factor in fancy coloured diamonds, colour is the most important. All other variables are forgiven when a diamond displays a well-saturated, rare colour. Brown diamonds are the most common followed by yellow. Yellow diamonds are readily available in larger sizes, even over 10 carats. Blue, green, purple, violet, orange, pink and red are rare.


Pure colours are the most desirable but most coloured diamonds are a blend of two or more colours called modifiers. A yellow diamond might be identified as Brownish Yellow or Orangey Yellow. There may be several modifiers such as Greyish, Purplish Blue.


GIA lists fancy coloured diamonds in several grades of intensity. Faint, Very Light and Light colour grades are assigned to any colour except yellow and brown; which fall into the lower end of the D-Z scale used for colourless diamonds. Fancy Light, Fancy, Fancy Intense, Fancy Deep, Fancy Dark and Fancy Vivid are the other grades in increasing order of intensity and value; although a Fancy Dark may be less desirable if it is too dark.


Natural vs Treated

Natural coloured diamonds are rare, and that is why they command such a steep price. There are several methods to treat diamonds to produce colour. Most modern treatment methods cannot be identified by the standard gemmological testing equipment found in stores. Sophisticated testing only found in major labs is required. Because of the possibility of treatments, it is essential that any coloured diamond being sold as natural be accompanied by a report from a well-known gemmological laboratory like GIA. Reports should be dated no earlier than the year 2000 because some treatments were undiscovered before that time. If there is no report, assume that it is treated. Selling a treated diamond as natural is fraud.


Treated diamonds, often called colour-enhanced diamonds, are a wonderful way for your customer to enjoy wearing a coloured diamond without the high prices. The most common treatments are irradiation and HTHP processing. There is nothing wrong with selling a treated diamond as long as you fully disclose the treatment.



The most common irradiated diamonds you will see are blue or blue-green diamonds. Off-colour, unattractive natural diamonds are exposed to various forms of radiation and then heated to produce beautiful coloured diamonds. Although typically in the blue hues, almost many colours can be created with this method. The stones are not radioactive and are perfectly safe. The colours are stable and permanent. Proper identification can only be made with sophisticated laboratory testing.



HTHP stands for High Temperature/High Pressure; the same technique used to grow synthetic diamonds. Most often seen in yellow hues, it can produce almost any colour. This treatment is also stable, permanent and reasonably priced. They are often used in smaller sizes mounted in jewellery as side stones. It is impossible to identify this treatment without advanced laboratory analysis.


Coated Diamonds

Coated diamonds are the least expensive colour-treated diamonds on the market. Similar to the coatings that produce popular stones like Mystic Topaz, these diamonds have a very thin colour film applied to the pavilion. Although possible in any colour, pinks are the most common. This treatment is not permanent. The coating can be destroyed when exposed to chemicals or a jeweller’s torch. It can be identified using a carbide scribe or even a pocket knife to scratch the coating. The tool will not harm the diamond itself, but any scratch marks are a sure sign of a coating.


Selling fancy coloured diamonds is an effective way to differentiate your store from the competition and increase your bottom line. Check them out when you go to the fall shows and give it a try.

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