Orthoclase Feldspar – Scotland

Orthoclase feldspar is a well known mineral and a common constituent found in many igneous rocks. It has two cleavage planes, which are at right angles to one another, resulting in the crystals breaking into rhombic forms and is the reason for its naming, being derived form the ancient Greek wording for “straight fracture.” It is often a shade of pink in colour, fairly hard, appearing at 7 on the Moh’s scale of hardness and has a vitreous lustre, which means it shines or reflects light. Orthoclase is commonly found in many granitic rocks, being one of the main constituent minerals, the other two being quartz and mica. It is also common in felsic rocks such as rhyolite. The crystals can vary in size and the largest one discovered to date was found in the Ural mountains, Russia, measured 10 x 10 x 4 meters and weighing around 100 tons. These particular mineral samples were collected by staff from Strathpeffer, Ross-Shire, Scotland, unlike our Norwegian material, the Scottish material has a much more pale pink colour to it, almost white. It is available in various sizes but with limited stock, each sample will come supplied in a card tray with an information label.