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Coloured Diamonds

Diamonds displaying natural colour are extremely scarce, only one in ten thousand diamonds mined will display natural colour due to the paucity of the exact conditions needed coupled with the required trace elements that will affect upon the carbon atoms during the growth of the diamond's crystal lattice and stimulate the colour change during crystallisation. This transformation occurs under intense heat and pressure about 100 miles down within the Earth's mantle, just above the Earth's molten core. Radiation will also impact on colour, particularly in the case of green diamonds.

Coloured diamonds exhibit colours from across the spectrum, in order of rarity - red, green, blue, pink then yellow & champagne coloured diamonds can be found amongst others, these colours are all attributable to the presence of nitrogen, hydrogen or boron. 'Chameleon' stones can also be found which are extremely rare and exhibit properties that can see their colour change under certain conditions, stones of primary colour, a singular colour such as 'pink' are more valuable than those with a secondary colour or hue, e.g. purplish-red or brownish-pink.

Colour saturation

Coloured diamonds are graded on their saturation, colour hue, tone and intensity. Clarity is not such an important factor upon value as it is in white diamonds. The stronger the intensity the more expensive the diamond will be. For example, when pink diamonds are being graded, the result and hence cost will be dependent on the depth and intensity of the 'pink' colouring, rather than the clarity (or internal cleanliness) which is a significant factor in grading white diamonds.

The Gemological Institute of America (GIA) uses nine different grades for the intensity in coloured diamonds.

G.I.A. intensity grading:

  • 1. Faint
  • 2. Very Light
  • 3. Light
  • 4. Fancy Light
  • 5. Fancy
  • 6. Fancy Dark
  • 7. Fancy Intense
  • 8. Fancy Deep
  • 9. Fancy Vivid

Pink Diamonds / Argyle Diamonds

Pink diamonds are amongst the world's rarest and most valuable diamonds. Western Australia's Argyle diamond mine owned solely by Rio Tinto is the world's principal source of pink diamonds, to put the true rarity of these special 'pink' diamonds into perspective, of every million carats of rough diamonds produced at the mine, a mere one carat is suitable for sale in a yearly tender, the Argyle mine only releases around 65 pink loose diamond stones each year to tender with a weight range up to 1 carat and another 50 - 100 stones of 'good colour' weighing from 0.5ct. The mine has been estimated to be operable only until 2018, thus, it is no wonder pink diamonds are a rare and wanted commodity.

Nature creates pink diamonds in shades ranging from subtle pastel rose to strong raspberry and powerful purple-reds.

The value of a pink diamond is determined by the intensity of its colour. The 4C's which determine a diamonds price (cut, colour, clarity and carat weight) apply just the same to all colours of diamonds; however very intense colours - no matter which colours - have a greater influence on a diamond's price.

Tremendous pressure exerted on a diamond deep in the earth can abnormally compress its structure, causing lattice misalignments and ruptured bonds that are a hallmark of all pink, red, brown and purple diamonds thus creating evidence of the graining which scientists believe is attributable to the huge pressures under the earth. This graining can be seen at 10x magnification in many Argyle pink and cognac diamonds, the presence of nitrogen is also important with lower levels inducing pink shades.

As with all coloured diamonds, pink diamonds / Argyle diamonds are graded according to the intensity of colour in each individual stone. Argyle Diamonds uses a scale from one to eight - being the reverse of that used by the 'G.I.A.' one being the most intense and valuable colour and eight the lightest.

The 1 to 8 grading is then given an additional grade according to each individual diamond hue.

Blue Coloured Diamonds

Blue diamonds are extremely rare. Many originate from the Cullinan diamond mine in South Africa which is the only notable blue diamond production mine. The Cullinan mine also produced the largest diamond of the De Beers Millennium jewels collection which is the brilliant vivid blue 'Heart of Eternity' diamond that is 27.64 carats in weight. The collection was on show at London's millennium dome throughout 2000, an audacious attempt to steal the collection was foiled on November 7th, 2000.

Another world famous blue diamond, the 'Hope' diamond, is 45.52 carats and is a fancy deep blue colour cut into a round brilliant shape. The 'Hope' diamond was the diamond worn by Kate Winslet in the movie 'Titanic' when she was painted as "Rose" by "Jack Dawson" (Leonardo DeCaprio). The movie Titanic played had a big impact in educating the public about blue diamonds.

Blue diamonds come in a wide range of shades from ice blue to a rich deep blue.

Accurate proportions are very important in blue diamonds as they are with any diamond. Proportion is such an important aspect of the "cut" of a diamond and even more so for coloured diamonds. Blue diamonds that are too dark because of bad proportion fail to reflect the maximum amount of light, the 'Hope' as an example had additional facets added later in it's life to further intensify it's brilliance and depth of colour.

All natural blue diamonds belong to a type 11b which are diamonds that have little or no nitrogen but boron which acts as an 'acceptor', boron transforms the lattice into a semi-conductor that absorbs red, orange and yellow light therefore they appear blue or grey or nearly colourless. Argyle blue or violet diamonds are not the result of boron impurities, nickel or high concentrations of hydrogen are believed to be responsible for the colouration in these diamonds.

With the closure of the Cullinan mine of South Africa, the source of nearly all Blue diamonds, the supply of these diamonds has simply stopped. The scarcity of Blue diamonds has caused the prices to sky rocket with unbelievable prices being paid by dealers.

At Christies in 1995 a 4.37ct Blue diamond sold for $2,486,000 ($569,000 per carat) setting a record for the most paid per carat. At Sothebys in 2007 a 6.04ct Internally Flawless fancy vivid blue diamond sold for $7,981,835 ( a staggering price per carat record of $1,321,590). The following month at Sothebys again a 4.16ct fancy vivid blue diamond sold for $4,727,986 ($1,136,535 per carat).

Blue diamonds are commanding large premiums in the market place at present and the prices seem only to be going upwards.

Yellow Coloured Diamonds

Many people believe that yellow diamonds are not as valuable as white or colourless diamonds but when very yellow it is a fancy yellow diamond and therefore it is very valuable, it is the off-white colours from colourless diamonds that are less valuable and should not be confused with yellow diamonds.

As with all coloured diamonds, the deeper and more intense the colour in the diamond the higher the value of the diamond will be. Yellow diamond colours range from a fancy intense vivid yellow 'canary' colour to a light yellow, depending on the concentration of nitrogen present when the crystal forms.

The Kimberley Octahedron is the largest rough yellow diamond in the world at 616 carats. It was discovered in South Africa in the Dutoitspan mine in about 1972.

A few well known purchasers of yellow diamonds include the musician Seal who proposed to supermodel Heidi Klum with a canary yellow diamond engagement ring and Elton John who wears a 25 carat yellow diamond ring.

The Argyle mine in Western Australia has produced a significant amount of yellow diamonds which are distributed around the world.

Green Coloured Diamonds

Pure Green diamonds are extremely rare as their natural green colour comes from exposure to irradiated particles over thousands of years. They are the second rarest colour after red. It can take a very long time to get a 'natural' certification for a green diamond from the Gemological Institute of America (GIA) .Treated green diamonds also get their colour from radiation introduced in the laboratory, sorting out which are real and which are natural gives the laboratories their toughest challenge to date.

Natural radiation impacting on already formed diamonds over millions of years can impart a green hue.

Black Coloured Diamonds

Black diamonds have become increasingly popular. Natural Black diamonds are very rare, very hard and beautiful. It takes five times as long to cut a black diamond over any other diamond. The best Black diamonds have a metallic caviar colour.

The Black Orloff, the Eye of Brahma weighing 67 carats is the most famous of the Black Diamonds.

Champagne Coloured Diamonds

Brown coloured diamonds have been marketed very effectively by the Argyle mine as Champagne, Cognac and Chocolate in colour. Their affordability is making them a popular choice for someone wanting a diamond of colour.

The 'Golden Jubilee' is largest and most famous brown diamond as well as the largest faceted diamond in the world, a 545.67 carat fancy-brown cushion cut. Discovered in 1985 at the Cullinan mine in South Africa, for years this stone was known as the "Unnamed Brown". It got its present name when it was presented to the King of Thailand in 1997 on the occasion of his Golden Jubilee. It is currently part of the crown jewels in the Royal Thai palace.

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