gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1967.036.277.19 Extinction Curves and Equivibration Curves Obtained with a Variable-Axis Spindle-Stage Villarroel H. Joel N. 1 Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 2777, Santiago, Chile

Present address of N. J.: Dept. of Natural Sciences, UNESCO, Place Fontenoy, Paris 7э, France.

 3 1967 36 277 127 130 8 7 1966 Copyright © 1967, The Mineralogical Society 1967 Summary

A modification of the one-axis spindle-stage for the study of the optical indicatrix of crystal grains on the polarizing microscope is described. It allows the crystal to be rotated around axes within a range of about 40° without having to remount it. Some advantages of this variable-axis spindle-stage for obtaining extinction curves and equivibration curves (n0 curves) are illustrated.