Pumpellyite from the Witwatersrand was found to be intensely zoned and to show exceptionally wide variations in optical properties. Refractive indices (βD) varied from 1.693 to 1.726, birefringences from .0016 to .0103 and optic axial angles (2Vx) from 38° [optic axial plane perpendicular to (010)] to 71° [optic axial plane parallel to (010)]. These angles again were dispersed through a wide range, showing r>v in the former case and r<v in the latter. The following axial elements were determined for the mineral: β = 70°, c/a=.842.

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