-------------------------------------------------------------------------------- Chemical Formula: Mg2Al3O Mineral Name: Iolite Color: Transparent, violet-blue, light blue, blue, rich blue-violet stone Hardness: 7.5 -------------------------------------------------------------------------------- Iolite is a silicate of alumina, iron, and magnesia, having a bright blue color and vitreous luster; cordierite. The name iolite comes from the Greek ios, which means violet. Iolite is a blue silicate mineral that occurs as crystals or grains in igneous rocks, only as a result of contamination of the magma by aluminous sediment. The property that made iolite so valuable to the Vikings is extreme pleochroism. Iolite has different colors in different directions in the crystal. The gemstone changes colors depending upon which angle it is viewed from. Iolite, known as the Vikings' compass, due to it's ability to determine the direction of the sun on overcast days. When the legendary Viking mariners sailed the wide ocean, they used thin pieces of iolite as the world's first polarizing filter. Looking through an iolite lens, they could determine the exact position of the sun, and navigate safely. Synthetic magnesium iolite has a low thermal expansion and is used as a semirefractory material because of its resistance to thermal shock. Iolite is artistically used in making necklaces, pendants, rings, bracelets etc. Iolite is commonly cut into traditional shapes, and its most desirable color is a rich violet-blue. It is found in the regions of Australia, Sri Lanka, Burma, India, Madagascar and Brazil.