A silicate of alumina, iron, and magnesia, having a bright blue color and vitreous luster; cordierite. It is remarkable for its dichroism, and is also called dichroite. A variety called Caribbean iolite has a lighter blue color.
(also called dichroite or water sapphire). A silicate of alumina, iron, and magnesia which is usually violet-blue, but can be deep blue, light blue-gray, and yellow-white. Makes a beautiful transparent gemstone which is remarkable for its dichroism.
It is a mineral which is used as a gemstone. It occurs in deep blue, purple, light blue-gray, and yellow-white.