abstract:Piemontite is a sorosilicate mineral in the monoclinic crystal system with the chemical formula Ca2(Al,Mn3+,Fe3+)3(SiO4)(Si2O7)O(OH). It is a member of the epidote group.
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a dark red mineral occurring in metamorphic rocks: a complex hydrated silicate containing calcium, aluminium, iron, and manganese. Formula: Ca2(Al,Fe,Mn)3(SiO4)3OH 红帘石