Fancy colour diamonds

I first became aware of fancy colour diamonds in the 1980’s a friend of mine who worked as a stone dealer showed me various shades, I was so taken with them I bought them all.

Back then they weren’t really well known by the public, but I thought they were beautiful, I had various shades of pink and yellow, ranging in size from small 1.5mm  to over a carat.  I wouldn’t be able to afford to buy them today !


In recent times they have become much beter know and well regarded, in fact the most expensive gem ever auctioned is The Pink Star diamond, 59.6 carat natural pink sold for £57.1 million at Sotheby’s in Hong Kong on March 29  2017. The Pink Star was mined by De Beers in an unspecified location in Africa in 1999. Originally 132.5 carats as a rough diamond, Sotheby’s says it was meticulously cut and polished over a period of two years

Diamonds in the normal colour range are colourless to light yellow and are described using  D-to-Z colour-grading scale.  Rare specimens come in every colour of the spectrum, including, yellow and brown, most rarely, blue, green, pink and red.

Only one in 10,000 diamonds has a fancy colour.

Colourless diamonds usually decrease in value as the colour becomes more obvious. Just the opposite happens with fancy colour diamonds: Their value generally increases with the strength and purity of the colour. Large, vivid fancy colour diamonds are extremely rare and very valuable. However, many fancy diamond colours are muted rather than pure and strong.

As with most things rarity equals value ( not always beauty!) With diamonds in the normal range, value is based on the absence of colour, because colourless diamonds are the rarest. With fancy colour diamonds—the ones outside the normal colour range—the rarest and most valuable colours are strong pinks, blues and greens. In all cases, even very slight colour differences can have a big impact on value.

Compared to fancy yellows and browns, diamonds with a noticeable hint of any other hue are considerably more rare. Even in light tones and weak saturation, as long as they show colour in the face-up position, qualify as fancy colours. Red, green and blue diamonds with medium to dark tones and moderate saturations are extremely rare.


Red diamonds are so rare that only a handful are known to exist. Unlike other colours, the red or pink tone is due to structure deformity, rather than impurities. Generally pink and red diamonds are pure carbon.

Diamonds with red or reddish colours are extremely rare and highly valued. Pure pinks are the most popular, and incrediably expensive. I really like the pink champagne tone, I think it’s a more sophisticated colour, which is much more affordable, and looks stunning when combined with rose gold and white diamonds. 

Blue diamonds are extremely rare. They generally have a slight hint of grey, so they’re rarely as highly saturated as blue sapphires. Their colour is caused by the presence of boron impurities—the more boron, the deeper the blue. Less than one boron atom per million of carbon atoms can give a diamond a blue colour. 

The De Beers Cullinan Blue is the largest blue diamond ever to be auctioned. It sold for just under £46M on April 27th this year at Sotheby’s Hong Kong – way above its £38m estimate, but just short of the Oppenheimer Blue’s £46.4m record.

The step-cut fancy vivid blue diamond weighs 15.10ct. Accompanied by GIA report no. 2223179803 stating that the diamond is Fancy Vivid Blue, Internally Flawless; also accompanied by a diamond type classification letter stating that the diamond is determined to be a Type IIb diamond. Type IIb diamonds are very rare in nature (…less than one half of one percent)…today the most significant source is limited to the Cullinan mine in South Africa…Among famous gem diamonds, the 70.21 carat Idol’s Eye and the 45.52 carat Hope are examples of Type IIb.

Green diamonds get their colour when radiation displaces carbon atoms from their normal positions in the crystal structure. This can happen naturally when diamond deposits lie near radioactive rocks, or artificially as a result of treatment by irradiation. Fancy green diamonds are typically light in tone and low in saturation. Often the colour appears muted, with a greyish or brownish cast. The hue is generally in the yellowish green category. In most green diamonds, the hue is confined to the surface, and rarely extends through the entire stone.

Brown is the most common fancy diamond colour and also the earliest to be used in jewellery. Second-century Romans set brown diamonds in rings. In modern times, however, they took some time to become popular.

Brown diamonds were not typically considered for jewellery until the 1980s, when they began to appear in the production of the Argyle mines. The brown tone can be caused by nitrogen, or nickel impurities as well as crystal deformation

Our queen is not the only royal to have a rare diamond collection. The Golden Jubilee Diamond, a 545.67 carat brown diamond, is the largest cut and faceted diamond in the world. And part of the Thai Crown Jewels, it outweighs the Cullinan I by 15.37 carats 

Yellow is diamond’s second most common fancy colour. Yellow diamonds are sometimes marketed as “canary”. While this isn’t a proper grading term, it’s commonly used in the trade to describe fancy yellow diamonds. The yellow is caused by the presence of nitrogen, the more nitrogen the stronger the colour.  I have some beautiful strong canary diamonds, but also think some of the paler lemon colour can be very pretty,  also the stronger golden tone works well in Platinum.

Until the late 1990s, there was not much demand for black diamonds. The colour is  caused by large quantities or clouds of minute mineral inclusions such as graphite, pyrite or hematite.  I like to use them as strings to put a pendent on, the sparkle they produce is stuning. They  look beautiful as a contrast with orange sapphires.

With fancy colour diamonds, colour is the dominant value factor. Even diamonds with numerous inclusions that result in a low clarity grade are prized by connoisseurs if they display attractive face-up colour. Of course, inclusions that threaten the gem’s durability can lower a fancy colour diamond’s value significantly. Fancy colour diamonds can exhibit colour graining, which is considered an inclusion.

treated diamonds

With anything of value, there is always someone trying to cut corners. With diamonds it involves what we call treatments. As a consumer, you will regularly encounter in the marketplace gems that have been treated to change their appearance.

Because these treatments are not always apparent to the unpractised eye, and are sometimes difficult to distinguish even by experts, it is necessary and legally required for anyone selling a gem to disclose any treatment procedure a gem may have received. Non-disclosure of this treatment could cause a person to believe that a particular gemstone was of higher quality naturally, and therefore more valuable than it actually is. One added challenge is that treatments can be permanent, long lasting or short-lived under normal jewellery use. Treated gems may require special care by their owner.

The most commonly encountered treatment of diamonds is irradiation. Neutron and electron radiation are the most common forms of artificial irradiation, and it is possible to induce black, green, blue green, deep yellow, orange, pink and red diamonds (often combined with a secondary step of heating, to achieve certain colours).

Heating diamonds at high pressures and high temperatures (HPHT) can remove or lessen their colouration so that the gem becomes colourless. Other types of diamond may be transformed from brown to yellow, orangey yellow and yellowish green, or to blue colours by this process.

Thin-film coatings are sometimes used on diamonds to change their colour. Crude yet effective coatings can also include the use of permanent ink markers along the girdle surface of a diamond, causing its face–up appearance to be affected by the colour of the ink used. More modern coating methods use thin films of metal oxide.


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