Garnet Peridotite

Garnet peridotite is a  coarse grained, ultra mafic igneous rock which forms at extreme depths within the earths upper mantle, over 40 Km in depth, as such, the rock is composed of high pressure, high temperature forming minerals such as olivine which gives the rock an over all green colouration of varying shades. (some appear lighter shades and some darker). Due to the depths and temperatures that this rock forms at, it contains little silica minerals such as quartz, less than 40%. As the name implies, the samples also contain a fairly sizeable amount of rich red garnet crystals as well which offers a striking opposition in colouration between the two main constituent minerals. Current dating suggests that this rock formed over 1.2 billion years ago and was brought up to the earths surface through tectonic activity, particularly the Caledonian orogeny, which was a large scale mountain building event which occurred between the Ordovician to Early Devonian period, 490–390 million years ago. This huge event occurred when the prehistoric ocean known as the Iapetus close due to the ancient continents of Laurentia, Baltica and Avalonia colliding, resulting in land masses along the borders colliding with one another across what is now modern day Scandanavia, the British Isles, Greenland and part of Northern Europe. The result was the large Caledonian mountain range spanning across the above mentioned areas which can still be visited to this day such as the Grampian highlands in Scotland. This huge event pushed up mantle material which contained the garnets and peridotites to the earths crust where weathering and erosion has since exposed pockets of them. These particular specimens come from the famous Gusdal olivine pit in Åheim, southern Norway and are excellent for collectors of all levels and ages due to the the vibrant colours the samples exhibits as well as for college and higher educational education, in which these specimens can be used to describe deep mantle rocks as well as orogenic processes (in this case the Caledonian orogeny) can result in such material being available at the surface. Specimens are available in various sizes and come supplied in a card tray with a label.