Usually black, also commonly light blue to blue-black, gray-blue, gray, brown
Streak
Pale gray to bluish-grey.
Luster
Vitreous, Sub-Vitreous
Refractive Index
n = 1.680 - 1.698 n = 1.683 - 1.700 n = 1.685 - 1.706
Diaphaneity
Translucent, Opaque
Cleavage
PerfectPerfect on
Fracture
Splintery
Crystal Habit：Prismatic, frequently very elongated. May be acicular, especially in late cavities. Sometimes is very acicular in fine-grained, light colored aggregates. Well-terminated crystals are uncommon.
Geological Setting：Syenite and undersaturated rocks
YueGongAnBei 44051102000467
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