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Black diamonds are found only in two regions of the world, viz. Brazil and Central African Republic, and they usually occur in alluvial deposits. Black diamonds never occur in Kimberlite and Lamproite pipes, and therefore they do not originate deep inside the earth like conventional diamonds. Not one black diamond has ever been discovered in the conventional Kimberlite diamond mines of South Africa, Canada, Australia or Russia. Even in the long history of exploitation of diamonds in the Indian Sub-Continent, the first diamond producing country in the world, the discovery of black diamonds have never been reported.
Some characteristic features of black diamonds
An interesting feature of black diamonds is that unlike conventional diamonds which are made up of a single massive crystal, they are made up of aggregates of perhaps millions of tiny crystals stuck together, giving it a porous nature. Apart from graphite, iron compounds such as hematite and magnetite may be associated with the conglomerate crystal, giving it the black color. Black diamonds are harder than conventional diamonds, because they do not have cleavage planes like conventional diamonds. Thus black diamonds are extremely difficult to cut and polish. However there may be areas in the black diamonds that are softer, due to loosely bound porous material. Hence working with black diamonds can pose serious challenges to the experienced diamond cutter, and drastic losses of weight are a usual occurrence in the cutting of black diamonds. The 300.12-carat Gruosi rough diamond had a weight of only 115.34 carats after it was processed, resulting in a loss of 184.78 carats. The Black Orlov that weighed 195 carats in the rough state, had a finished weight of only 67.50 carats. The 587-carat Spirit of de Grisogono rough diamond had a final processed weight of only 312.24 carats.
The Amsterdam Black Diamond is the largest monocrystalline natural black diamond in the world
According to a certificate issued by the Gem Tech Lab Geneva bearing No.
10237 and dated September 27, 2001, the Amsterdam Diamond is a rare monocrystalline black diamond, whose coloration is natural caused by the presence of small graphite grains mainly located in its feathers. Feathers are cracks or fissures in diamonds that resemble the design of feathers. It must be remembered that graphite is also an allotrope of carbon, like diamond, but with contrasting properties such as being soft and brittle, and an electrical conductor, instead of being hard and tough and a non-conductor as diamonds. If the Amsterdam Diamond is monocrystalline it is like any other conventional diamond, and not a conglomerte crystal made up of millions of tiny crystals like other black diamonds. At the time the Amsterdam rough diamond was cut in 1972, by the master cutters of D. Drukker & Son, the cutting appears to have been executed very carefully, without generating excessive heat, that would have created pyrolitic graphites, which could have intensified the black color of the diamond, and possibly interferred with its unique adamantine luster. If the certificate issued by the Gem Tech Lab Geneva is accepted, the Amsterdam black diamond is without doubt the largest monocrystalline natural black diamond in the world.
Interesting history of the Amsterdam diamond's discovery
The Amsterdam Black diamond was discovered in South Africa in the early 1970s. The discovery of the diamond was accidental. The rough diamond was originally part of a large piece of mine bort, discarded and set aside to be broken up into smaller pieces, before being crushed into diamond powder. The term "bort" is usually applied to refer to all rough diamonds, which for some reason or another are unfit for use as gems, and include irregular groupings of diamond crystals. The diamond owes its discovery to the alertness of the cleaver/crusher, who was impressed by the unusual hardness and the intense black color of the piece of rough diamond. He reported the discovery to his supervisor, and the rough diamond was added to the collection of gem-quality rough diamonds, suitabe to be cut and processed as finished diamonds. It was around this time that the agent of the Amsterdam diamond merchant and cutters, D. Drukker & Sons, visited South Africa, and was show this unusual black stone. He examined the rough stone, and purchased it from the mine owners, for an unspecified amount. The diamond was then taken to Amsterdam and after detailed studies by the master cutters of the company, it was decided to cut it as a pear-shaped diamond, the best possible shape that would bring out the intrinsic beauty of the stone. The number of facets in the pear-cut diamond was also significantly increased, compared to the standard pear-cut, a deliberate decision, perhaps to increase the adamantine luster of the stone.
Percentage loss of weight in processing the Amsterdam diamond is relatively low compared to other black diamonds, a possible indicator of the diamonds monocrystalline nature.
During the process of cutting and polishing, the weight of the diamond was reduced from 55.85 carats to 33.74 carats, a loss of around 40% of the original rough weight, comparable to other conventional diamonds. This loss is fairly reasonable when compared to losses in other black diamonds, such as Gruosi diamond - 60% loss, Korloff Noir - 70% loss, Black Orloff - 65% loss and Spirit of Grisogono - 49% loss. The difference is perhaps due to the nature of the black diamonds, Amsterdam diamond being monocrystalline like conventionl diamonds, whereas the other diamonds are all polycrystalline carbonados. Losses in carbonados are usually much greater than in conventional diamonds.
Sale of the Amsterdam Diamond by Christie's Geneva on Novemner 14, 2001
While the Amsterdam black diamond remained the property of D.Drukker & Zn. Amsterdam, it was exhibited in its pendant sitting, in their stores in the City, and was also given on loan for many exhibitions around the world. The exhibition of the diamond in many countries served to raise awareness among the public, that diamonds can not only exist in almost all colors of the rainbow, but also as black diamonds, a fact not known and appreciated by many people around the world.
In the year 2001, it appears that D. Drukker & Zn.decided to dispose of their treasured possession, the black Amsterdam diamond. The pear-shaped diamond was removed from its pendant mount, and assigned to Christie's Geneva to be sold at their Magnificent Jewels Sale to be held on November 14, 2001.
The Christie's auction catalogue for the sale
described the diamond as an unmounted modified pear-shaped fancy black diamond weighing 33.74 carats, in a blue leather fitted case. The diamond was accompanied by three certificates issued by reputed institutes testifying to its credentials. One certificate bearing No.
10565041 issued by the Gemological Institute of America, and dated January 18, 1999, testifies to the authenticity of the diamond as a natural colored fancy black diamond. A second certificate issued by the Gubelin Gemological Laboratory, bearing No.
9911078 and dated December 6, 1999, confirms the previous finding by GIA that the diamond is a natural colored black diamond. A third certificate issued by the Gem Tech Lab Geneva bearing No.
10237 and dated September 27, 2001 confirms the two previous findings that the diamond is a natural colored black diamond. The third certificate was accompanied by an annex with the following information :-
This historic diamond called the Amsterdam is one of the very few monocrystalline black diamonds that can be described today as: "of natural coloration".
Why three different independent assessments of the black diamond's credentials became necessary ?
The necessity for three different independent assessments of the stones credentials can be appreciated because it is a well known fact that white diamonds can be colored black, either by irradiation or high temperature annealing. Natural black color in diamonds is caused by black inclusions such as graphite and iron. When white diamonds are exposed to a higher dose of irradiation, a deep dark green color is produced, that appears black. High temperature annealing involves natural diamonds being heated to a very high temperature under low oxygen concentrations, that favors the carbon in the diamond to change phase towards graphite, at least on the surface, imparting a black color to the diamonds. Thus, in natural black diamonds inclusions are scattered throughout the stone, whereas in heat-treated black diamonds the inclusions are concentrated near the surface. In heat treated black diamonds the black color is produced by the lining of graphite near the surface, formed as a result of the treatment. Hence in testing monocrystalline diamonds for their natural black color, it becomes necessary to exclude irradiated black diamonds and high temperature annealed black diamonds.
The Amsterdam Diamond achieves a price per carat of US$ 10,220, the highest price per carat achieved by a black diamond at an auction
Christie's placed a pre-sale estimate of $302,000 to $391,000 on the Amsterdam diamond, at its Magnificent Jewels Sale 1290, held in Geneva, on November 14, 2001. After a keenly contested bidding, the diamond was sold to an anonymous buyer for $344,837, which works out to $10,220 per carat, the highest price per carat paid for a black diamond at an auction. This is much higher than the price per carat achieved for another black diamond sold previously at an auction - the 489.07-carat, rectangular-cut, black diamond that sold for US$1.7 Million, working out to $3476 per carat.
Fawaz Gruosi founder and president of de Grisogono, who popularized black diamond jewelry after 1996
Fawaz Gruosi is credited with the popularization of black diamond jewelry, marketed under the brand name De Grisogono
The current popularity of black diamond jewelry is credited to Fawaz Gruosi, who inspired by a photograph of the Black Orlov diamond set with contrasting white diamonds, which he accidentally saw in a magazine in 1996, swung into action, and took a world tour scouting for black diamonds in the main diamond producing areas of the world. Having collected enough of these under-rated stones, he got them processed by black diamond cutting experts based in Antwerp, who transformed the stones into jet-black beauties. Using these diamonds Fawaz, turned out a breathtaking collection of jewelry, consisting of necklaces, earrings, bracelets, and rings. To bring out the contrast in colors he always associated the black diamonds with other gemstones such as white diamonds, gray icy-diamonds, pearls, rubies, emeralds, sapphires etc. The jewelry were marketed under the famous de Grisogono brand name, and became an instant success. The black diamond jewelry became very popular among women, and Fawaz Gruosi is credited with launching the love affair between the black diamond and women around the world.
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Related :-
1) Black Orlov Diamond
2) Gruosi Diamond
3) Korloff Noir Diamond
4) Spirit of de Grisogono Diamond
References :-
1) Christie's Magnificent Jewels Sale 1290, Geneva, November 14, 2001 - Online catalogue, The Amsterdam Diamond - Lot Description. www.christies.com
2) Christie's Magnificent Jewels Sale 1290, Geneva, November 14, 2001 - Online catalogue, The Amsterdam Diamond - Lot Notes. www.christies.com
3) Fancy Colored Black Diamonds - Diamond Source of Virginia, Inc. www.diamondourceva.com
4) Diamond properties, geology, exploration, mining - Part III. www.minelinks.com/alluvial/diamonds
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