Diorite

Diorite is a medium to coarse grained intrusive igneous rock with an intermediate chemistry, meaning that it is composed mainly of silicate minerals, such as plagioclase feldspar, biotite mica, as well as other typical dark coloured igneous minerals such as hornblende and pyroxene, though minor amounts of muscovite mica may also be present but is often not visible with the naked eye. Chemically, diorite falls between mafic rocks and felsic and is often an off white colour with a greenish tint which form a backdrop for the dark iron bearing minerals. Due to its phaneritic texture and coarse grain size, it is described as being speckled in appearance making the rock often sought for due to the contrast in colours. These particular samples come from Cockermouth in Cumbria and are believed to have formed as intrusive plugs within the Skiddaw group, the rock is known locally as Embleton diorite with radiometric dating suggesting that the rock formed approximately 444 million years ago during the Ordovician period. This rock, which is technically a micro-diorite, is suitable for collectors and higher level education to describe various forms of igneous rocks, the chemistry and mineralogy, the samples are available in three sizes and come supplied in a card tray with an information label.