Syenite – (Larvikite)

Larvikite is an igneous plutonic rock and a variation of monzonite as it is composed mainly of feldspar minerals, specifically the three endmember ones, orthoclase, albite and anorthite, with sizes of crystals being over 2 cm in size giving the rock a coarse grained texture. Plagioclase is also present in the rock in some quantity and it is the alternating layers between the orthoclase and plagioclase which gives the rock a blue/silver shimmering effect, best visible when a face has been cut and polished, which is known as a schiller effect, (or labradorescence). These particular specimens were collected by staff and come from Larvik in Norway and form part of the Larvik Plutonic Complex in the area. This complex is a suit of 10 igneous plutons which were emplaced in the Oslo graben, a large rift event which occurred between the end of the Carboniferous and the start of the Permian period known as the Variscan orogeny. This orogeny was caused when huge continental collision took place between Euramerica (Laurussia) and Gondwana to form the super continent, Pangaea. The rock has been dated to the Permian period, between 292 – 298 million years old and was found from its type locality of Larvik. Due to its naturally eye catching appearance, striking blue schiller and hard wearing properties, this rock is extremely sought after for numerous uses such as building facing stones, counter tops, gravestones and many more. The samples are ideal for all manner of collectors both due to its rarity in the world and notable appearance as well as for educational use at various levels as it will surely garner interest from younger pupils due to its colours as well as its mineralogy and texture being suitable to teach higher level students. Specimens are available in three sizes and come supplied in a card tray with an information label.