Neptunite - KNa₂LiFe²⁺₂Ti₂Si₈O₂₄

Habit: Black. Prismatic crystals, typically with square cross-sections, and may be curved or twisted. Vitreous luster; nearly opaque. Brown streak.

Environment: Occurs in natrolite veins cutting a glaucophane schist inclusion in a serpentinite body.

Etymology: Named for Neptune, the sea god of Roman mythology, because of the close association of its type occurrence with aegirine, the name of which derives from Ægir, the Scandinavian sea god