Peridotite is a dense, coarse grained, ultramafic igneous rock consisting largely of olivine and pyroxene. Typically containing less than 45% silica & high in magnesium. Peridotite is derived from the Earth's mantle either as blocks & fragments or from crystallisation from magma generated in the mantle. The name peridotite is derived from the gemstone peridot consisting of pale green olivine which is an ultramafic mineral. Classic peridotite is bright green but can range in colour from yellow to red & brown, the rock is also very common in the sauna industry as they appear to hold heat extremely well, generate an incredible amount of steam and also return to their original form when cooled, where as other rocks tend to contract, expand and even crack when subject to such extreme changes in temperature. These specimens come from Finland and are on offer in three optional sizes, the specimen supplied will come in a card tray with an information label.