Piemontite is a sorosilicate in the monoclinic with the chemical formula Ca2(Al,Mn3+,Fe3+)3(SiO4)(Si2O7)O(OH). group.
Red to reddish-brown or red-black in colour, Piemontite has a red streak
The type locality is the Prabornaz Mine, in Saint-Marcel , Italy
It occurs metamorphic rocks of the greenschist metamorphic facies and in low-temperature hydrothermal veins. It also occurs in metasomatized ore, tremolite, quartz