A New Method for Orthoscopic Adjustment with the Fedorov stage

A. F. Hallimond
75 Corringham Road, London, N.W. 11

Summary: A new method is described to replace the standard procedure for completing the adjustment of an optical symmetry plane, with conditions for the accurate use of the biquartz. Extinction measurements are plotted to show the wide range of sensitivity (for the adjustment of A1 and A2) at various directions in the symmetry planes of a plagioclase. It is proposed that A1 and A2should be adjusted at different settings of A4 so as to obtain maximum sensitivity for each of those axes.

Mineralogical Magazine; September 1959 v. 32; no. 246; p. 245-250; DOI: 10.1180/minmag.1959.032.246.07
© 1959, The Mineralogical Society
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