Rough diamond embedded in its kimberlite host rock, an igneous rock in which diamonds can form at great depth under intense pressure and high heat. Type location is the Kimberly mines area, South Africa. Most diamonds are produced by open pit mining of the host rock. A number are found in streams and seashore deposits, where they end up after uplift and weathering out of their host rock. Diamond, composed of pure carbon (atomic symbol C), is the hardest naturally occurring substance known. Most diamonds are used industrially, only the pure and larger specimen are applied in jewellery. This diamond measures 12 mm across.