Determination of 2V from One Extinction Curve and Its Related n0 Curve

N. Joel
Centro de Investigaciones de Cristalografía, Instituto de Física y Matemáticas, Universidad de Chile, Casilla 2777, Santiago, Chile

Summary: From the extinction curve of a biaxial crystal mounted on a spindle stage (or one-axis stage goniometer), the related n0 curve can be derived and drawn on the stereogram. The n0 curve is the equivibration curve—or constant-refractive-index curve—that goes through the projection P0 of the spindle-stage axis. After the principal diameters (maximum 2η and minimum 2ζ) of the no curve have been measured, the angle 2V may be calculated by means of the formula cos V = sin ζ/sin η. This method can also be used for determining—or refining—the directions of the principal axes α, β, γ.

Mineralogical Magazine; December 1963 v. 33; no. 263; p. 679-692; DOI: 10.1180/minmag.1963.033.263.05
© 1963, The Mineralogical Society
Mineralogical Society (