Description of Mineral Diamond is a crystalline form of carbon.
Natural diamond is the hardest known mineral.
The common crystalline form of diamond is an octahedron but also occurs as cubes and irregular masses. The largest diamond recovered to date weighs 0.985 carats. Individual bulk sample grades up to 23.4 carats per 100 tonnes have been reported. They are transported to surface by kimberlite or lamproite volcanic magmas. They are also found in placer deposits , where diamonds have been concentrated in river gravels and beach sands, as they were liberated by erosion of diamond bearing kimberlite and lamproite rocks.