Colour is a very important factor in diamond grading, or more correctly absence of colour. Most diamonds are graded on a whiteness scale or absence of colour scale. While most diamonds are in the colourless to light yellow range, some have a natural colour that is deep, distinct, and opulent. These are known as fancy-colour diamonds and are often blue, brown, or pink. Unlike colourless and near-colourless diamonds which are valued for their lack of colour, fancies are valued for the intensity of their colour.
Over recent years coloured diamonds have become increasingly sought and expensive. But how does colour come about and how does it affect the price?
What Causes Colour in Diamonds?
Diamonds are very pure carbon that crystallised more than 100km beneath the earth's surface. Diamonds grow under immense heat and must be transported to the surface within an hour or two in a volcano. In a way they are snap frozen; if the journey takes too long they revert back to graphite or carbonaceous gases.
Sometimes other atoms are trapped in a diamond as it grows or during its violent ride to the surface. The most common is Nitrogen; the tiniest amount causes blue light to be absorbed giving the diamond a yellowish colour. Argyle diamonds, mined in Australia, are an exception as they are actually very pure; the cause of the rare pink colour is a freak of nature and also unfortunately means they have many more inclusions than most diamonds from other sources. The worry is that once the Argyle mine runs out of pinks, the diamond world will be a less colourful place.
Pink and Red Diamonds
Before the discovery of the Argyle diamond mine, most pink diamonds were a pastel shade worthy of passing interest, but not lasting passion. This all changed in 1985. The Argyle mine in the far north of Western Australia, produces almost all of the world's red and pink diamonds, although they only make up a tiny part of the mine's production.
Until 2009, the huge open cut mine has been the world's largest diamond mine in total carat weight. In 2007 RioTinto decided to start an underground mine because the open cut has become too deep taking too long for the trucks to drive down the spiral pit – the smaller output from the underground mine will greatly reduce the availability of pink diamonds, and probably drive-up the already high prices.
Pink diamonds cost from 5 to 100 times as much as colourless diamonds.
Scientists do not fully understand the cause of the pink colour. Usually colour is caused by impurities, but Argyle diamonds are very pure. They are found in a rock called Lamproite that appears to have had a particularly violent journey through the earth's crust. (All other diamonds were transported to the earth's surface in a rock called Kimberlite).
This unique host rock and the transition to the surface means it is unlikely another mine like Argyle will ever be discovered. So once the underground mine at Argyle dries up, in around 2017, it's sayonara pink diamonds!
Argyle Tender
Argyle offers its finest 50 or so pink diamonds each year in a sealed bid tender. In some years the tender includes a red and, occasionally, a blue diamond. The event has become widely reported.
The tender opens in Perth before a week in Hong Kong, Tokyo, Mumbai, New York, London and finally Geneva where the bids are opened. Prices usually exceed US$100,000 per carat. Many of the world’s rich and famous are the eventual owners. It is said the Sultan of Brunei has a standing bid of US $1million for any red diamond bigger than 1ct. Apparently he is building a collection that will one day appear as a magnificent suite of jewellery. Some of the diamonds are still waiting underground in Western Australia.
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Champagne Diamonds
Champagne or brownish coloured diamonds are the most affordable coloured diamonds, at around one third the price of white diamonds. This good buying will not last forever and Argyle champagne diamonds have some unique features.
Prices for colours C1 (lighter) to C6 (the colour of cognac) are all about the same. Lighter stones are popular because they sparkle more and cost less than pure colourless. More intense colours are also popular because they are more unusual, so supply and demand are balanced.
You can simply choose the colour you like best without worrying about which is more valuable. However there are many different secondary colours and this is important. In general warmer colours are more attractive than grey-greenish browns (indicating the diamonds have not come from Argyle). Intense golden and rusty colours are called Fancy Cognac, or C7 and cost a little more because they are quite rare. (The French cognac people do not allow the use of their word – but the champagne people like the idea!)
Naturally champagnes with a pinkish tinge are the most sought after and expensive. Champagne diamonds (and most other coloured diamonds) are often more heavily included than white diamonds.
Blue Diamonds
Natural blue diamonds are a light greyish blue shade, a more "steely" colour than sapphire. The most famous blue diamond is The Hope diamond in Washington's Smithsonian Institute. This stone is steeped in legends of horrible deaths that befell many of its owners, from guillotining during the French Revolution, to a Wall Street broker jumping to his death in 1930.
New York jeweller Harry Winston purchased it to donate to the Smithsonian and only owned it for one day. While his insurance company and armed couriers were discussing the cost and method of delivering the priceless gem to Washington, it’s reported that Harry strolled down to the post office and posted the diamond in a cigarette packet as ordinary mail!
Green Diamonds
Green diamonds have come in contact with radioactive minerals such as uranium. Radiation stains the outside of the diamond, so the cutter must be careful not to cut away too much of the green "skin". Authenticating that the radiation occurred naturally requires laboratory analysis at a leading gemmological institute. Buyer beware!
Yellow and Orange Diamonds
To be called a Fancy Colour means the diamond has more colour than Z on the GIA D-Z white diamond grading scale. Fancy yellow diamonds come in a range of hues from greenish yellow to amber. They start at similar prices to white diamonds and prices raise with increasing intensity.
Connoisseurs in the trade use the term "canary" to describe intense yellow. Burnt orange Argyle champagne's are a less expensive alternative to very expensive pure gold or orange colours.
The Ellendale mine, discovered about the same time as Argyle, has been opened and operating for the past several years and it has produced many fine fancy yellow diamonds.
White-Milky Diamonds
A little known and quite rare diamond is a white opalescent diamond. These are collector's oddities. They are much less expensive than transparent colourless diamonds.
Black Diamonds
Pave' set Black diamonds are popular in high-fashion jewellery and are often used in men's jewellery. Most of the black diamond fashion jewellery is made with irradiated treated coloured diamonds. Natural untreated black diamonds with a good surface luster are rare. Many other black diamonds are low clarity diamonds that when heated go very dark grey.
Rarity
Intensely coloured diamonds are the rarest and most beautiful of nature's gem treasures. Rarity and desire are the two things that set the price of coloured diamonds. The most rare and prized in order are red, blue, pink, green, gold and then yellow, milky white, champagne and black. Values can be 100 times more than that of a white diamond!
The long standing highest price per-carat ever paid was $1,250,000 for a 6mm purplish-red badly flawed 0.90ct diamond of just less than 1 carat (inclusions are common in natural red and pink diamonds). It was named the Hancock Red.
In May 2009 this record was surpassed when a flawless vivid blue diamond weighing 7.03 carats sold for a record $9.49 million, the highest price paid per carat for any gemstone.
Colour is a very important factor in diamond grading, or more correctly absence of colour. Most diamonds are graded on a whiteness scale or absence of colour scale. While most diamonds are in the colourless to light yellow range, some have a natural colour that is deep, distinct, and opulent. These are known as fancy-colour diamonds and are often blue, brown, or pink. Unlike colourless and near-colourless diamonds which are valued for their lack of colour, fancies are valued for the intensity of their colour.
Over recent years coloured diamonds have become increasingly sought and expensive. But how does colour come about and how does it affect the price?
What Causes Colour in Diamonds?
Diamonds are very pure carbon that crystall