Piemontite
A variety of Minerals
What is Piemontite?
Piemontite is a sorosilicate mineral in the monoclinic crystal system with the chemical formula Ca2(Al,Mn,Fe)3(SiO4)(Si2O7)O(OH). It is a member of the epidote group. Red to reddish-brown or red-black in colour, Piemontite has a red streak and a vitreous lustre. The type locality is the Prabornaz Mine, in Saint-Marcel, Aosta Valley, Italy. It occurs metamorphic rocks of the greenschist to amphibolite metamorphic facies and in low-temperature hydrothermal veins in altered volcanic rocks. It also occurs in metasomatized deposits of manganese ore. Associated minerals include: epidote, tremolite, glaucophane, orthoclase, quartz and calcite.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Piemontite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
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Quick Facts
Physical Properties
- Color
- Red, red-violet, red-brown to reddish black
- Hardness (Mohs)
- 6 - 6.5
- Rock tumbling
- With care
- Density
- 3.45 g/cm³
- Streak
- Reddish
Chemical Properties
- Chemical Formula
- {Ca2}{Al2Mn3+}(Si2O7)(SiO4)O(OH)
- Elements
- Al, Ca, H, Mn, O, Si
Also Known As
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Piemontite FAQs
How do I identify Piemontite?
Piemontite can be identified by its hardness of 6 - 6.5 on the Mohs scale, Red color. Look for these key characteristics when examining specimens.
What color is Piemontite?
Piemontite typically appears in Red, red-violet, red-brown to reddish black. Color can vary depending on impurities and formation conditions.
How hard is Piemontite?
Piemontite has a hardness of 6 - 6.5 on the Mohs scale. This gives it moderate hardness.
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