Diamond Mines

 

 
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Diamond Mines


Diamonds are formed by high-pressure high-temperature (HPHT) processes that naturally occur deep within the Earth. The exact temperature and pressures at which these processes occur naturally is not known, but we can get a pretty good idea by comparing the temperatures used when using artificial HPHT means to manufacture synthetic diamonds. It seems that temperatures of approximately 5000°C and pressures of around 100,000 atmospheres are needed - and such temperatures and pressures occur nowhere on the surface on the Earth, nor anywhere in the outer layer of the Earth, known as the crust.

It is thus thought that natural diamonds are created within the Earth's mantle (this view is reinforced by the fact that a pressure of 100,000 atmospheres is equivalent to that of 200 miles of rock). Most of the diamonds formed in this way, probably never reach or approach the surface, but just sometimes they are exploded towards the surface in fissures. These fissures tend to become circular near the surface, are known as "pipes", and are composed of the mineral kimberlite.

White diamond on kimberlite:
White diamond on kimberlite

In some diamond mining regions, diamonds are mined directly from the kimberlite pipes. However, kimberlite, like other minerals is liable to weathering and erosion, and hence in other diamond mining regions, diamonds may be found in locations where the alluvial deposits from erosion are found - such as beaches, deltas, river and stream beds, and former river and stream beds.

Here is a list of some the most important diamond mining regions around the world:
  • South Africa - South Africa became famous for diamonds in the 19th century when diamonds were first found on the banks of the Orange River. Today, South Africa contains many famous diamond mines, including Bultfontein, Dutoitspan, Jagersfontein, Premier, and Wesselton, and is a world leader in diamond production, although larger stones seem to be becoming more scarce. The majority of the diamond mines in South Africa (as well as many of South Africa's gold mines, are today owned by De Beers which is part of Anglo American, a large conglomerate.

    Alluvial diamond mining in Sierra Leone:
    Alluvial diamond mining in Sierra Leone
  • Other African Countries - In addition to South Africa, many other African countries also contain sources of diamonds:
    • Angola - Produces high-quality gemstones, but production interrupted many times in recent years by civil war and political problems.

    • Botswana

    • Central African Republic - Alluvial deposits in gravel beds.

    • Côte d'Ivoire - Alluvial deposits.

    • Democratic Republic of Congo - Alluvial deposits.

    • Ghana - Alluvial deposits in gravel beds, mostly producing industrial diamonds but some of gem quality.

    • Guinea - Alluvial deposits.

    • Lesotho

    • Namibia - Large deposits on the Atlantic coast near the mouth of the Orange River.

    • Sierra Leone - Alluvial deposits in river gravels that often produce very large and high-quality diamonds.

    • Tanzania - Large pipe found in 1935, which has produced some high-quality diamonds.

    • Zimbabwe - Known for alluvial depositrs.

  • India - India was the world's principle source of diamond for most of recorded history, and many famous diamonds originate from the subcontinent. Indian diamonds are generally alluvial, and diamonds are found in conglomerates, gravel and sandstone deposits. Diamond mines are found in Andhra Pradesh, Golconda, Kollur, and some other regions.

  • Brazil - Brazil produces many diamonds, but few diamonds of gem quality, although a occasionally a large high-quality gem stone has been found in the country. Diamonds are found in several Brazilian states including Bahia, Matto Grosso, and Minas Gerais.

  • Borneo (Malaysia) and Indonesia -Some small alluvial deposits have been found in this region, and the diamonds produced are generally small (less than 1 carat).

  • Venezuela - Venezuela is a significant source of alluvial diamonds, often yellow-colored

  • Russia - Russia is a major source of diamonds, and several hundred pipes have been found in the country. Most Russian diamonds are very small in size, so are not particularly valuable. Additionally, as all Russian pipes are found in Siberia, adverse weather conditions can make mining difficult, dangerous, and expensive.

  • Australia - In the 1970s it was realized that parts of Australia contain some regions with very similar geology to that of South Africa's diamond region. A group named Ashton Joint Venture Partners therefore began to search, and duly found both kimberlite pipes and rich alluvial deposits of diamonds in Australia. As a result of these finds, Australia is estimated to contain a substantial proportion of the world's known diamond reserves, and expected to eventually become the world's largest diamond producer. However, as diamonds from Australia tend to be small and low in quality, South African diamond will probably continue to dominate the market for gemstones.

  • United States of America - Only one significant diamond deposit is known in the USA - at Crater of Diamonds State Park near Mursfeesboro in Arkansas. The Crater of Diamonds State Park site is on state-government owned landed so has never been fully developed - instead tourists can pay a fee to dig on the surface. In addition to Mursfeesboro, some alluvial diamonds have been found in the United States.

  • Canada - The alluvial diamonds found in the United States were long believed by some to originate from pipes in Canada, and the diamonds were thought to have been brought southwards by Canadian glaciers, but for many years no Canadian pipes were known. This all changed in 1991, when two geologists, Chuck Fipke and Stewart Blusso, found evidence of pipes in the Northwest Territories - these pipes were developed into what eventually became the EKATI mine, which produced Canada's first commercial diamonds in 1998. More prospectors followed, and soon (by 2006), three major mines (EKATI, Diavik, and Jericho), were producing well over 10 million carats of gem quality diamonds each year. As a result, Canada leapt from being nowhere in the world diamond production league, to being the third largest producer of diamonds in the world.

    Diavik Diamond Mine:
    Diavik Diamond Mine

    Jericho Diamond Mine:
    Jericho Diamond Mine





 
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