Putnisite

Putnisite has unique chemical and structural properties, and does not appear to be related to any of the existing mineralogical families. Crystals are translucent purple, but show distinct pleochroism (from pale purple to pale bluish grey, depending on the angle of observation) and leave pink streaks when rubbed on a flat surface.

Putnisite occurs as small (< 0.5 mm) cube-like crystals in volcanic rock. The mineral formed during the oxidation environment within komatiite to dioritic bodies containing sulfide minerals.