Cummingtonite
Chemical Formula	(Mg,Fe)7Si8O22(OH)2
Species	Silicates
Crystal System	Monoclinic
Mohs Scale	5-6
Specific Gravity	3.1-3.6
Color	Dark green, brown, gray, beige; colorless to pale green in thin section
Streak	nd
Luster	Vitreous
Refractive Index	n = 1.639 - 1.671 n = 1.647 - 1.689 n = 1.664 - 1.708
Diaphaneity	Translucent, will transmit light on thin edges.
Cleavage	Perfecton
Fracture	Splintery
Crystal Habit：Rarely as distinct crystals. Columnar to fibrous and granular