Piedmontite is a distinct, manganese-bearing member of the epidote group, easily recognized by its vibrant reddish-pink to violet color. It is typically found as prismatic crystals or fibrous masses within regional metamorphic rocks and manganese-rich hydrothermal deposits.
Is this piedmontite?
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 piedmontite with a known reference. Piedmontite sits at Mohs 6-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: reddish-pink.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: red, reddish-brown, pink, violet.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, radial aggregates, fibrous, massive.
Often confused with
Piedmontite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Piedmontite leaves reddish-pink, Epidote leaves grayish white.
How to tell apart: Streak differs, so Piedmontite leaves reddish-pink, Clinozoisite leaves grayish white.
How to tell apart: Streak differs, so Piedmontite leaves reddish-pink, Allanite leaves gray; luster reads vitreous on Piedmontite and submetallic on Allanite.
Often found alongside piedmontite
Minerals reported to co-occur with piedmontite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Al₂(Mn³⁺,Fe³⁺)(SiO₄)(Si₂O₇)O(OH)
- Mohs hardness
- 6-7
- Density
- 3.4-3.5 g/cm³
- Streak
- Reddish-pink
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals, radial aggregates, fibrous, massive
- Cleavage
- Perfect basal
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- metamorphic rocks, specifically manganese-rich schists and hydrothermal veins
Where rockhounds find piedmontite
1 mapped spotsClassic worldwide localities
- San Quirico, Italy
- Piedmont, Italy
- Hakone, Japan
- Ojo Caliente, USA
- Gloucestershire, United Kingdom
Field-hunting tip
Where it forms: metamorphic rocks, specifically manganese-rich schists and hydrothermal veins. If you start seeing quartz, calcite, tremolite in float, you are in the right ground. Typical habit: prismatic crystals, radial aggregates, fibrous, massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Pennsylvania. Start trip planning there.
More piedmontite photos
Common questions
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What rocks look like piedmontite?+
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Find piedmontite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
