Diamonds are entirely made of Carbon atoms crystallised in a cubic (isometric) arrangement. Most natural diamonds are formed at high-pressure high-temperature environments existing at depths of 140 to 190 kilometers (87 to 120 miles) in the Earth mantle. Diamond deposits are termed Kimberlites, Pipes or Blue Ground. These are also called Primary Mines. In contrast, diamonds are also found at river beds and are termed Alluvial Deposits.