Piemontite
Chemical Formula	Ca2(Al,Mn3+,Fe3+)3(SiO4)(Si2O7)O(OH)
Species	Silicates
Crystal System	Monoclinic
Mohs Scale	6
Specific Gravity	3.45
Color	Reddish-brown, reddish-black
Streak	Red
Luster	Vitreous
Refractive Index	n = 1.725 - 1.756 n = 1.730 - 1.789 n = 1.750 - 1.832
Diaphaneity	Translucent, Opaque
Cleavage	PerfectPerfect on Poor on
Fracture	Irregular/Uneven
Crystal Habit：Slender prismatic, blocky to massive
Geological Setting：Greenschist to amphibolite grade regional metamorphism, metasomatised manganese deposits, low temperature hydrothermal veins.