Optica rotation axes in a manganoan richterite from the Taguchi mine, Aichi Prefecture, Japan

Abstract

Conoscopic observations and measurements were made in visible and infrared light on a manganoan richterite from the Taguchi mine, Aichi Prefecture, Japan. The angle 2σ between the two rotation axes of one pair could be calculated. It is inferred that the remarkable discordance between the polarization and absorption axes gives large 2σ angles even in amphiboles having a small absorption coefficient K (of the order of 10^-4).