HomeIntroduction to Diamonds

History of Diamond

The earliest productive mines were in the Golconda region of India, particularly along the Kristna River. After 1725 this mining district was gradually eclipsed in importance by the diamond deposits of Brazil. Diamonds were first mined there along the Jequitinhonha River, in the Diamantina area of the state of Minas Gerais.

 

In 1867 a 21-carat stone was discovered on the banks of the Orange River near Hopetown, South Africa. A great diamond rush started, and new deposits were discovered that were more productive than any the world had ever known. Another major diamond resource was developed in the 1950s in the Yakutia region of the Soviet Union. By the 1980s the Yakutia and South African regions and the country of Zaire dominated the world's diamond market. The mineral has also been found in smaller amounts in numerous other places. In the United States the leading producers include Arizona, Nevada, and Montana, although the largest gemstones have been found in an eroded volcanic pipe in Pike County, Ark.

For many years, microscopic diamonds have occasionally been noted in meteorites; they were attributed to high-speed collisions in space or with the Earth. In 1987, however, following the discovery of many more such diamonds, the theory was developed that they are the product of ancient supernova explosions of giant stars.

In recent years, diamonds have been found in unusual metamorphic rocks that were subjected to very high temperatures and pressures.

Diamonds were first discovered in India, probably around 800 B.C.
Until 1725, India’s market city of the diamond trade, Golconda, was fabled to be the source of these gems. In fact, these diamonds were mined in the surroundings of this city. Smaller quantities also came from Kalimantan (Borneo).

The primary volcanic source of these gems was never discovered during the almost 2500 years in which the Indian sub-continent was the only producer of diamonds. These alluvial deposits were rich enough to supply the world until the eighteenth century.

Before the Portuguese discovery of a direct sea route to India, diamonds reached Venice by two Mediterranean routes: a southern route by way of Aden, Ethiopia and Egypt; and a northern route, through Arabia, Persia, Armenia and Turkey.

A diamond-cutter’s guild was established in Antwerp., helping this city flourish as a diamond center with vast supply of rough arriving from Lisbon as well as from Venice, and later from London, as the English fortified their interest in India in the late 1600’s. Only one exception: after the attacks on Antwerp in 1585 by the Spanish army, many diamond cutters moved to Amsterdam.
Diamond craftsmen, many of them Jews fleeing religious persecution in Spain, Portugal, Germany and Poland, were attracted by the liberal policies of the Netherlands. But a change in fiscal policies in the Low Countries caused diamond cutters and traders to move back to Antwerp..
Today, this city handles more than 80% of the world’s rough diamonds, as well as half of its polished diamonds, continuing thus a tradition of over 500 years of cutting and trading.

Diamonds rough and cut As the Indian production started to wane, diamonds were discovered in 1725 in Brazil. These deposits were able to maintain a steady supply of small stones after 1730.
Large quantities of significant size stones appeared on the market only with the exploitation of the South African diamond fields from 1866 onwards. The discovery of these deposits also led to the first sudden increase in supply. This increase coincided with the new wealth generated by the Industrial Revolution and the corresponding rise in the demand for luxury goods by a broader range of consumers.

South Africa's alluvial diamond deposits were discovered near the Orange River.
Further exploration in the Kimberley region revealed for the first time volcanic formations called "pipes" filled with an unknown type of rock that contained diamonds. This rock, a variety of peridotite, was named "Kimberlite" after the region of its first discovery, was recognized as the diamond’s source. Only Western Australian diamonds have a different source, which is a closely related rock type, lamproite.

The discoveries in South Africa led to a rush of prospectors staking out numerous claims. Mining by hazardous open-pit operations prevented rational exploitation of the diamond fields. In 1889, Cecil Rhodes and Barney Barnato bought out these claims and merged their interests in De Beers Consolidated Mines, Ltd. in South Africa, establishing a monopoly on the diamond trade that remains today.

In 1992, a whole new field of diamantiferous kimberlite pipes was discovered in the Northern Transvaal, and in 1993 production has moved to a peak of 5 millions carats, scheduled to be maintained for the next 20 years.Nevertheless, on the world market the South African diamond output is today rivaled by exploitation of the major deposits that were found in Australia, today the world’s main producer with an output average of over 25 millions carats annually, approximately 25 % of annual world production.

Worldwide famous, the Australian Argyle mine was able to produce 42 millions carats in 1994. Other pipes in the same region are under evaluation. The Argyle mine is also famous for the high percentage of yellow and brown material, known also under the name of “Champagne” and “Cognac,” and the constant recovery of a small amount of pink to red stones.

This pink to red material is sold as cut stones in private auctions, or “tenders”. Viewings are held annually in New York, Sydney, Hong Kong, Tokyo, London and Geneva, where polished pink diamonds with an average weight of about one carat, typically achieve prices in the 100 000 USD per carat. To put the rarity of these diamonds into perspective, about one carat in one million produced in this mine is suitable for sale at these auctions.

Yellow diamond oval cut Since 1829, diamond production has also begun in Russia with the discovery of alluvial diamond deposits in the Northern part of the Ural Mountains. But it was not until 1954 that abundant kimberlite pipes were discovered in the permafrost of Yakutia, Siberia. Yakutia adopted in 1992 a new Constitution, and was renamed the Republic of Sakha. This Republic is today another leader in diamond mining: it produces 99% of Russian diamonds, accounting to 20% of the world diamond mining.

The Russian diamond mining and processing industry, at the initiative of the government, is developed without foreign participation.
Its main deposits are situated in the Western part of Sakha (990 thousand square km), where 18 kimberlite fields were found. Uduchnaya, Mir, Aikhal, Internacionalnaya, Jubileinaya diamond pipes, are well known around the world, earning to this vast region in the Sakha Republic the name of “the diamond province”.

South Africa is not the only producer in its continent. Many alluvial deposits or kimberlite pipes have been found in other countries, especially Namibia, Angola, Botswana, the Democratic Republic of Congo (formerly Zaire), Tanzania, Ghana, Sierra Leone, Liberia, Gabon, Cameron, the Central African Republic and Zimbabwe.
Botswana with its Orapa mine, produce yearly and average amount of 5 Millions carats, while the Kalahari Desert Jwaneng mine produces 6 millions carats per year.
Democratic Republic of Congo (formerly Zaire) with its production of mainly low grade and industrial quality is the second biggest world diamond producer after Australia.
Angola, another important diamond producer, exports up to 2 millions carats of good quality annually, but its uncertain political situation has hindered organized mining and prospecting. With the recent peace underway, there is no doubt that Angola will be a big player in the international diamond market.
Ghana has always produced more diamonds than the other West African countries but for the most part these stones are much smaller. Their value per carat varied from 10 to 20 USD compared 250 to 300 USD for stones from Sierra Leone where large and exceptional quality diamonds are produced since 1935.
Liberia, a small size producer from the end of the 90’s represents a special case. Many of the diamonds exported from this country until mid 2002 are the so-called “blood diamonds” or “conflict diamonds”. This appellation means sold by rebels and governments to fund their war campaigns, principally in Sierra Leone. To a broader extend, these names were also applied to diamonds from Angola and the Democratic Republic of Congo.

The international community, concerned about the increasing negative impact on the consumer, took measures, signed in Interlaken, Switzerland, by more than 50 nations involved in the diamond trade to stop this diamonds for weapons trade.
The resulting agreement, known as the Kimberley Process, started since January 1, 2003. It proposes an independent certification expert system for tracking rough diamonds origin.
But recent peace treaty between belligerents in Angola and the withdrawal of foreign armies in Democratic Republic of Congo will hopefully put an end to this trade.

Diamonds are also found in the United States in Arkansas, California, Colorado, and North Carolina.
In 1990, extensive diamond pipes were found in Canada's Northwest Territories. Today Western Canada is the site of the world's newest diamond rush.

Diamond cutting centers are found all over the world, most notably in Belgium, India, Israel, South Africa, Thailand, China and the USA.

16.1.1 Discovery and Mining developments

Diamond recovery is important in understanding and identifying diamonds as the process of recovering diamonds can help identify a country of origin. The two recovery processes are that of Pipe or Mine deposits and Placer deposits.

Pipe or Mine deposits are found in the source rock itself and the rock that the diamonds formed in is crushed to free the diamonds within it. At present this is how diamonds are mined in Canada. The source rock is known as kimberlite and in simple terms is a volcano that bust to the surface of the earth cutting through several layers of rock to reach the surface. In doing so it carried chunks of rock from the layers that it cut through and within these chunks of rock are found the diamonds. The kimberlite cools and what is left is a ìpipeî that extends in the shape of a cone into the earth, with the wide end of the cone at the surface. The diamonds in these mines have not been exposed to erosion or weathering process and as a result are typically angular in shape showing classic crystal shapes with clearly defined faces and edges. However, in limited cases diamonds may have been exposed to radiation and this can alter the appearance of the diamond in terms of its shape and surface features. As a further note there is another type of commercially viable source rock known as Lamphorite that like kimberlite can contain diamonds. Diamoniferous lamphorites of commercial viability are much more rarer than kimberlite however some exist including that at the Australian Argyl Mine.

Placer deposits are deposits of diamonds which have been moved from their original source rock to another place through the process of erosion and other forces of nature. Often Placer deposits are found in river beds, on beaches, or sea floors. The diamonds in these cases have been freed from the Kimberlite through erosion and transported by wind, water or gravity to a likely resting place in a river bed, sea floor or beach. Millions of years of erosion of the kimberlite remove enough diamonds that a concentration of them can build up in another place, forming a placer deposit. Although diamonds are the hardest mineral it is subject to weathering as is any other mineral. As the diamond is transported from the kimberlite pipe it may be scratched or bumped along the way. Depending on the terrain, the distance the diamond is moved, and the time involved, the diamond may have its edges worn down and rounded like any other stream pebble. A diamond found in a placer deposit will show varying degrees of rounding from very slight to that similar to polished round stream pebble.

The potential for placer deposits of diamonds in Canada are unlikely as recent glaciation would not lend itself to the formation of placer deposits due to the limited time that has gone by since the last glaciation. Placer deposits formed prior to the glacial period would likely have been scraped away by the glaciers and scattered over such a large area that although a single gem may be found it is extremely unlikely that a second one would be found in the vicinity. The exception perhaps would be within glacial till deposits which are concentrations of glacial sediment that could be a source of a placer deposit. The writer is unaware of any placer deposits of gem quality diamonds in Canada.

The following is a list of diamond producing countries and generalized recovery types.

South Africa Pipe and Placer

Zaire Pipe and Placer

Namibia Placer (beach)

Angola Placer (river)

Ghana Placer (river)

Guinea Placer (river)

Ivory Coast Placer (river)

Liberia Placer (river)

Sierre Leone Placer (river)

Russia Pipe and Placer (minor deposit)

Australia Pipe

Canada Pipe

  • Diamonds and The Northwest Territories, Canada.

Given the forgoing, in general it could be said that gem quality diamonds produced in Canada originate in Pipe Mines and therefore the roughs would appear angular and have a marked absence of weathering. http://www.cigem.ca/ross/rough.html

 

 

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