New Techniques for the Universal Stage. II. The Determination of the 2V When Only One Optic Axis is Accessible

N. Joel and I. D. Muir
Crystallographic Laboratory, Cavendish Laboratory, University of Cambridge
Dept. of Mineralogy and Petrology, University of Cambridge.

Summary: When one optic axis of a biaxial crystal has been located accurately by the usual orthoseopic or conoscopic methods, the second may be located by determining the extinction positions at normal incidence and applying the Biot-Fresnel construction. When use is made of the extinction directions associated with two or more wave normals inclined to the section, this method gives more reliable values of the optic axial angle than can be obtained by the doubling of the angle V over the pole of a bisectrix. If the optic axes have been located with sufficient accuracy by this procedure, then this also determines the orientation of the indicatrix.

Mineralogical Magazine; June 1958 v. 31; no. 241; p. 878-882; DOI: 10.1180/minmag.1958.031.241.06
© 1958, The Mineralogical Society
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