Augite andesite igneous rock specimens from Thirlmere, Cumbria, UK which are of late Ordovician age which form part of the Barrowdale volcanic group. The samples are of intermediate composition and contain phenocrysts of the pyroxene mineral, augite, giving the normally dark blue rock a black speckled appearance. The samples are available in 3 sizes and come supplied in a card tray with a label.
Augite andesite is a variant of the fine grained igneous rock, andesite which contains coarse grained phenocrysts of augite crystals. An extrusive rock of intermediate composition, containing between 50 to 63% of silica, the samples have a dark colour with a blue tint while the augite crystals provide a speckled black appearance. The rock is estimated to have formed during the late Ordovician period and forms part of the Barrowdale volcanic group with other rocks such as dacite and basalt also being present in the area as part of a pre-caldera formation. The rock is slightly denser than our regular line of andesite due to the added pyroxene crystals of augite as phenocrysts. Ideal for established collections and higher level education to exhibit the presence of phenocrysts in igneous material, the rock samples come from Thirlmere, Cumbria, UK and are available in 3 sizes and come supplied in a card tray with a label.