Key Characteristics: The mineral's lack of color, bird's eye extinction and high birefringence are all diagnostic 2V: 2Vx = 28 - 47° Relief: Moderate positive relief; Small change in relief upon stage rotation Cleavage: One perfect cleavage Colour and Plechroism: Colorless in thin section Optical Orientation: Parallel and birds eye extinction Twinning: Not common Optical character: Biaxial (-)
