Článek: diamond mining... 19. 9. 2013

diamond mining

Diamonds originated in the Earth’s distant geological past in a remarkable way. Approximately one billion years ago from a depth of about 200 km a bedrock called kimberlite was thrown up to the earth’s surface by eruption. Under the unique conditions inside these narrow volcanic chimneys, during a rapid decrease in pressure and temperature, a crystallisation of diamonds occurred. At the present time similar conditions for the emergence of diamonds in nature no longer exist. Deposits of diamonds, the hardest mineral in nature, extend over the earth’s surface in places where precisely these old kimberlite pipes occur. Australia, Angola, Botswana, South Africa, Namibia, Russia and Zimbabwe are the main sources and world producers of diamonds. Diamond extraction is concentrated in primary and secondary deposits. Primary diamond deposits are indeed the Kimberlite pipes, mined to great depths (the Big Hole mine in South Africa is 500 metres wide, over 1,000 metres deep and is the largest hole ever dug out by man). However, out of every two hundred kimberlite pipes discovered, one at the most contains diamonds. Secondary diamond deposits arose from the effects of erosion with the deposits being subsequently carried away by river and sea; in Namibia diamonds are even successfully extracted from the seabed. Secondary deposits are more easily extracted and contain a high concentration of good quality diamonds. This is why in Zimbabwe all secondary deposits belong to the state; only primary deposits are offered to foreign developers for extraction. In 1985 the well-known diamond prospector Chuck Fipke discovered the last diamond deposits of interest in the Canadian Arctic, which are accessible only in the winter months. The Ekati and Diavik diamond mines with four kimberlite pipes today produce six million carats annually, while 30 per cent of the diamonds extracted prove to be of investment quality.