Variations in Chemical Composition and Optie Properties in Rhombic Pyroxenes

Abstract

There is urgent need for more accurate variation diagram of the optic properties with FeSiO3 content in the orthorhombic pyroxenes., The writer attempted to construct the diagram on the basis of the most credible date at present (as listed in the Table I) and obtained the rather successfull result as shown in the Fig., 1., The intensity of influence of Al2O3, CaO, Na2O, K2O, and TiO2 to the refractive index and optic angle was also discussed and estimated approximately as follows : Al2O3 (for Al replacing Mg) : 1% increases the refractive index about 0., 004-0., 007., Al2O3 (for Al replacing Si) : 1% increases it about 0., 002., When Na2O is rich (>0., 2%±), the influence of Al2O3 is much little., CaO (for Ca replacing Mg) : 1% decreases st about 0., 002., CaO (for Ca replacing S1) : 1% decreases it about 0, 002., Na2O : 1% decreases it about 0., 001-0, 01 K2O : 1% increases it about 0., 004., TiO2 : 1% increases it about 0., 008., Fe2O3 (as FeO) / Total FeO : 0., 1 decreases it about 0., 005., The factor decreasing the refractive index may increase the optic angle about X., The detailed discussion should be done refering to the studies on the mother rocks as well as the microcomponents.,