Aegirine
Chemical Formula	NaFe3+[ Si2O6]
Species	Silicates
Crystal System	Monoclinic
Mohs Scale	6
Specific Gravity	3.50-3.60
Color	Dark Green, Greenish Black
Streak	Yellowish-grey
Luster	Vitreous
Refractive Index	n = 1.720 - 1.778 n = 1.740 - 1.819 n = 1.757 - 1.839
Diaphaneity	Transparent, Opaque
Cleavage	Distinct/GoodGood on
Fracture	Irregular/Uneven
Crystal Habit：Prismatic crystals may be in sprays of acicular crystals, fibrous, in radial concretions
Geological Setting：Common in alkalic igneous rocks, carbonatites, and pegmatites; from regionally metamorphosed schists, gneisses, and iron formations; in blueschist facies rocks, and from sodium metasomatism in granulites; authigenic in some shales and marls.