ABNORMAL OPTICAL PROPERTIES OF BABINGTONITE FROM THE YAKUKI MINE, JAPAN

Abstract

Abnormal optical properties of babingtonite from the Yakuki mine, Japan, are described. Sections cut nearly normal to each of the optic axes of this mineral show no extinction. This is probably due to elliptic vibration of light which passes through the sections. Dependence of the ellipticity on the orientation of the section was determined. Interference figure exhibited by sections cut nearly normal to one of the optic axes is anomalous, especially remarkable for red light. The mineral absorbs light of different colour in different amount. Dependence of the optical density on the wave lengths of light is shown by variation curves.