Today, the most important diamond supplying countries are Australia and Congo for industrial diamonds and Southern Africa, Australia, Congo, Russia, Namibia and Botswana for gem quality stones. The mining methods are very diverse, depending on how diamonds present themselves at the earth's surface. When freed by erosion from the Kimberlite matrix, diamond crystals are carried along by rivers. Riverbeds are dug away and the river silt is sieved. Finding diamonds can thus be the result of large industrial operations, but also of small-scale methods, or even manual labour.
Diamonds are rare.
It is usual that 250 tons of rock, sand and gravel must be processed to yield one carat of diamond. The quality of a diamond is determined by the four C's. Carat , Colour, Clarity and Cut. A diamond can be graded for quality in a certificates laboratory HRD Certificates Lab . Diamonds are weighed in carats.