Piemontite
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| Piemontite | |
|---|---|
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| General | |
| Category | Sorosilicates, Calcium minerals, Aluminium minerals, Manganese minerals, Hydroxide minerals |
| Chemical formula | {Ca2}{Al2Mn3+}[O|OH|SiO4|Si2O7] |
| Identification | |
| Color | Reddish-brown, reddish-black |
| Crystal system | Monoclinic |
| Cleavage | One perfect, one poor |
| Fracture | Uneven |
| Tenacity | Brittle |
| Mohs Scale hardness | 6 |
| Luster | Vitreous |
| Birefringence | δ = 0.025 - 0.076 |
| Dispersion | r>v very strong |
| Pleochroism | Visible |
| Streak | Red |
| Density | 3.5 |
Piemontite is a sorosilicate mineral in the monoclinic crystal system with the chemical formula {Ca2}{Al2Mn3+}[O|OH|SiO4|Si2O7].[1] It is a member of the epidote group.[1]
Red to reddish-brown or red-black in colour, Piemontite has a red streak and a vitreous lustre.[1]
It has a brittle fracture, one perfect and one poor cleavage, and a density of 3.5 and a Mohs hardness of 6.[1]
The type locality is the Prabornaz Mine, in Saint-Marcel, Aosta Valley, Italy.[1]
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