Rough, natural diamonds are often hidden in dark grey or black volcanic rock, named 'kimberlite', which is also known as ‘blue ground’. Because the rock is located in an unlimited depth and comes with a great speed towards the earth’s crust, it forms crater pipes. The name 'kimberlite' is derived from Kimberley, a town in South Africa, named after Lord Kimberley, at the time, the British Colonial Secretary, where diamond discovery was enormously high. Australia and Russia are also known as prominent sites for diamonds.