Volcanic rock While still dominated by silicates, more primitive volcanic rocks have mineral assemblages with less silica, such as olivine and the pyroxenes. Bowen's reaction series correctly predicts the order of formation of the most common minerals in volcanic rocks. Occasionally, a magma may pick up crystals that crystallized from another magma; these crystals are called xenocrysts. Diamonds found in kimberlites are rare but well-known xenocrysts; the kimberlites do not create the diamonds, but pick them up and transport them to the surface of the Earth. Volcanic rocks are named according to both their chemical composition and texture. Basalt is a very
Buffalo Head Hills kimberlite field Buffalo Head Hills kimberlite field The Buffalo Head Hills kimberlite field is a group of kimberlitic volcanic pipes or diatremes in north-central Alberta, Canada. As of 2011, 41 kimberlite pipes, of which 28 are diamondiferous, had been identified in the field. They were emplaced during Late Cretaceous to early Paleocene time. As of 2014 the Buffalo Head Hills field is in the exploration stage and has not gone into production. The highest grade kimberlite pipe (Pipe K252) has an estimated grade of 55 carats per hundred tonnes. The Buffalo Head Hills (BHH) kimberlite field is part of the Northern Alberta