- Piemontite
Infobox mineral
name = Piemontite
category = , , , ,
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formula = {Ca2}{Al2Mn3+} [O| OH| SiO4| Si2O7]
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color = Reddish-brown, reddish-black
habit =
system = Monoclinic
twinning =
cleavage = One perfect, one poor
fracture = Uneven
tenacity = Brittle
mohs = 6
luster = Vitreous
polish =
refractive =
opticalprop =
birefringence = δ = 0.025 - 0.076
dispersion = r>v very strong
pleochroism = Visible
fluorescence=
absorption =
streak = Red
gravity =
density = 3.5
melt =
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references =Piemontite is a
sorosilicate mineral in themonoclinic crystal system with the chemical formula {Ca2}{Al2Mn3+} [O|OH|SiO4|Si2O7] . [http://www.mindat.org/min-3208.html Mindat reference page for Piemontite] ] It is a member of theepidote group.Red to reddish-brown or red-black in colour, Piemontite has a red streak and a vitreous lustre.
It has a brittle fracture, one perfect and one poor cleavage, and a density of 3.5 and a
Mohs hardness of 6.The type locality is the Prabornaz Mine, in Saint-Marcel,
Aosta Valley ,Italy .References
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