Drawing method for variation curves of extinction angle using spread sheet-type calculation soft wear

Abstract

Extinction angle can be calculated with using spherical trigonometry and Biot-Fresnel's law. The variation curves of extinction angle are useful for the determination of twinning laws, estimation of angle between crystallographic axis and optic elastic axis, and analyses of petrofabric. This paper describes how to draw the variation curves of extinction angle using spread sheet-type calculation soft ware in a personal computer.