Arfvedsonite
Chemical Formula	[Na][Na2][(Fe2+)4Fe3+][(OH)2|Si8O22]
Species	Silicates
Crystal System	Monoclinic
Mohs Scale	5-6
Specific Gravity	3.3–3.5
Color	Black, deep green on thin edges
Streak	Deep bluish gray, gray-green
Luster	Vitreous
Refractive Index	n = 1.652 - 1.699 n = 1.660 - 1.705 n = 1.666 - 1.708
Diaphaneity	Translucent, Opaque
Cleavage	PerfectPerfect on
Fracture	Irregular/Uneven
Crystal Habit：Fibrous, radial prismatic aggregates
Geological Setting：Alkalic granites and other alkalic rocks