Piemontite

General Information: Chemical Formula:Ca2(Al,Mn,Fe)3(SiO4)3(OH) = Ca2(Mn,Fe)Al2(SiO4)(Si2O7)O(OH) Composition:(Molecular Weight = 488.18 gm)Calcium 16.42 % CaManganese 10.13 % MnAluminum 9.95 % AlIron 3.43 % FeSilicon 17.26 % SiHydrogen 0.21 % H Oxygen 42.61 % O  Empirical Formula: Ca2Al1.8Mn2+0.9Fe2+0.3(SiO4)3(OH) Environment:Contact metamorphic rocks. Locality:Piedmont, Italy. Name Origin:Named after its locality.Physical Properties: Cleavage:[001] Good, [100] Distinct Color:yellow, carmine red, red, reddish brown, or reddish black. Density:3.4 Diaphaniety:Translucent Habits:Blocky - Crystal shape tends to be equant (e.g. feldspars)., Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline)., Massive - Granular - Common texture observed in granit e and other igneous rock. Hardness:6-7 - Orthoclase-Quartz Luminescence:Non-fluorescent. Luster:Vitreous (Glassy) Streak:redMore details...

Ca2(Al,Mn,Fe)3(SiO4)3(OH)