The optic axial angle of a crystal mounted on a spindle stage may be simply calculated from (a) either of two angle pairs that may be easily measured on the scales of the microscope and spindle axes during the process of orienting Y and either X or Z for index of refraction measurements and (b) the angle between an optic axis and the microscope axis when the optic plane is vertical, determined by means of Mallard's method. No stereographic plotting is required. Although probably not as accurate, the method is much faster than the various extinction-curve methods of determining 2V.

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