A variety of plagioclase feldspar which has a flashing display of varied colours suggestive of the Northern Lights. Although it has a dirty-grey colour before being cut, the cut stones, when placed ina certain position (but no other) before the viewer, change tremendously, acquiring a metallic lustre and a beautiful sheen, due to the lamellar composition and the property of adularescence, which inthis stone is called 'labradorescence'.The usual colour is blue, but a variety (called 'spectrolite') found in Karelia, Finland, shows the colour of the spectrum. The stones are usually cut with a flat surface, and have been carved ascameos. The original source, c. 1770, was the island of St. Paul, Labrador.