Piemontite is a manganese-rich member of the epidote group, easily distinguished by its distinctive reddish-brown to cherry-red color. It typically forms in low-grade metamorphic rocks and is highly prized by collectors for its rare, well-terminated prismatic crystals or vibrant massive chunks found in alpine-type veins.
Is this piemontite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch piemontite with a known reference. Piemontite sits at Mohs 6-6.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Piemontite leaves a reddish-brown streak.
- 3Read the lusterHold the specimen under a strong light. Piemontite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: red, reddish-brown, pink, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, massive, granular.
Often confused with
Piemontite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Piemontite leaves reddish-brown, Epidote leaves white.
How to tell apart: Streak differs, so Piemontite leaves reddish-brown, Allanite leaves gray; luster reads vitreous on Piemontite and submetallic on Allanite.
How to tell apart: Streak differs, so Piemontite leaves reddish-brown, Clinozoisite leaves white.
Often found alongside piemontite
Minerals reported to co-occur with piemontite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Mn³⁺Al₂(Si₂O₇)(SiO₄)O(OH)
- Mohs hardness
- 6-6.5
- Density
- 3.4-3.6 g/cm³
- Streak
- Reddish-brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Massive, Granular
- Cleavage
- Perfect
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Metamorphic Rocks, Specifically Manganese-rich Schists and Marbles
- Typical price
- $10-50 per specimen depending on crystal size and quality
Where rockhounds find piemontite
Classic worldwide localities
- Saint-Marcel, Italy
- Jakobsberg, Sweden
- Oman
- Japan
- California, USA
Field-hunting tip
Look in metamorphic rocks, specifically manganese-rich schists and marbles country, the host setting where piemontite typically forms. If you start seeing quartz, calcite, braunite in float, you are in the right ground. Field specimens usually show a prismatic crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find piemontite on the map
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