Coloured diamonds - fire and ice

The incredible rarity, beauty and value of fancy coloured diamonds make them favourites with collectors and investors



10 April 2013

“A diamond is forever” neatly expresses the lofty position of diamonds in the gem industry. Their prestige has never wavered over the centuries. But the world of diamonds also includes stones of rich and gorgeous natural colours. Let’s discover the mysterious natural coloured diamonds, coveted by collectors all over the globe.

Since the 15th century, when the Belgian Louis Van Berquem invented a cutting method that enhanced the dazzle of gemstones, diamonds have been inextricably linked to human history. Today, marketing has made diamond-collecting a passion that cuts across national boundaries, gender and age. In this article, we would like to introduce you to another side of the diamond family: coloured diamonds. Their history can be traced back to the ancient Indian empire, when they were used as a tribute to the gods in the temples. In the 18th century a French jewellery merchant, Jean-Baptiste Tavernier, completed a long journey to bring an uncut 115-carat blue diamond back to Europe, where it was sold to Louis XIV, king of France. Under the king’s command, it was re-cut into a 67.125-carat blue diamond, named the French Blue. Since then it became part of the French royalty’s jewellery treasures. After the French Revolution, the Blue Diamond was stolen and disappeared for two decades, resurfacing when it was purchased by the rich London banker Thomas Hope. By this stage it had once again been re-cut to 45.52 carats, and it subsequently became known as the Hope Diamond. After many changes of hands, the rare dark blue diamond was purchased in 1949 by New York jeweller Harry Winston. Nine years later he donated it to the Smithsonian Institution. The intricate history of the Hope Diamond shows just how closely these gemstones are connected to mankind.

Ordinary consumers are generally not aware of the value of coloured diamonds, because they represent only a very small portion of the total diamond production. They can be found in South Africa, India, Australia and Brazil. Colour in natural diamonds is created by impurities, present in tiny proportions, or defects in the crystal’s lattice structure.

Today, about 12 types of fancy coloured diamonds are recognized, with nine different colour shades in naturally-occurring diamonds. The most common type is yellow diamond, caused by the inclusion of nitrogen atoms. While the Gemological Institute of America (GIA) classifies low-saturation yellow and brown diamonds as in the normal colour range, adding a colour grading scale, white diamonds have their own 4C grading scale. The intensity and quality of colour determines the value of a stone, ranging from the highest level, fancy vivid, through to fancy intenseand fancy light. A stone’s GIA certificate indicates the level of its natural colour, from which its value can be determined.

Blue diamonds, relatively rare, are discoloured by boron impurities. The Hope Diamond is an example, but its size of 45.52 carats makes it extremely unusual, because blue diamonds are usually small. Blue diamonds are also divided into several different grades of colour: for example, the Hope Diamond is greyish-blue. After centuries, this particular stone is still unique in the world.

Pink diamonds are the result not of impurities, but of changes in the molecular lattice structure that are still not entirely understood by scientists. In any case, pink diamonds are very rare, more so than other coloured diamonds, and their prices have hit record highs in auctions over the last few years.

The most expensive pink diamond in the world is a 24.78 carat pink diamond ring, which fetched $46 million at a Sotheby’s auction in 2010. Pink diamonds are coveted by collectors, and they are amongst the best performers in auctions. Their attraction depends on their colour, but preferences change, and each auction affects market prices. David Morris Asia Development Manager Paul Redmayne-Mourad said, “The pink diamond is one of the hardest to price among coloured diamonds. At every auction, the price attained immediately determines the new market value of pink diamonds, and so they attract even more attention from collectors in recent years.” The most prized type is the purplish-pink diamond. If this particular colour is classified as fancy intense, it becomes a genuine treasure.

The rarest coloured diamonds of all are red diamonds, possibly unheard of by the general public. Up until today, less than 30 are known to exist in the world, the largest of which reaches five carats. The colour of red diamonds is also caused by changes in the molecular structure. A red diamond is always a collector’s dream. In 1987, the 0.95-carat Hancock Red Diamond, discovered in Brazil, was auctioned for $880,000 at Christie’s, a record high of $926,000 per carat. This record remained unbroken for over 20 years. Mr. Hancock had purchased his red diamond for just $13,500 in 1956. Because of their rarity, red diamonds are hard to find in ordinary jewellery stores or auction houses. Though their prestige among collectors is unparalleled, there are no accepted standard definitions of their colour. Consequently they are assessed in terms of Hancock Red Diamond standards, considered as being the best colour of all. Secondary colour classifications are not applied to red diamonds. Their absolute value places them right at the top of the fancy coloured diamonds scale.

According to Redmayne-Mourad, “In recent years, coloured diamond prices have been rising exponentially, fuelled particularly by Asian collectors in search of pink and blue diamonds.” The value of coloured diamonds cannot be determined from charts or tables, because they depend primarily on auction prices. Preferences for colours change with nationality: Asian collectors prefer pink diamonds, those from the Middle East like yellow, while in the United States there is a preference for blue diamonds. Geographical factors therefore also affect the value of coloured diamonds and their investment potential. We advise collectors to explore ceaselessly in order to have a chance of snatching up the crown of an auction.

Info box:
Say it with coloured diamonds
What created the shades?
Nitrogen – yellow
Boron – blue
Changes in the molecular structure – pink or red