Petitjeanite is a rare bismuth phosphate mineral typically found as small, thin, platy crystals in oxidized zones of hydrothermal deposits. Collectors often find it associated with other bismuth minerals in complex pegmatite environments, requiring magnification for detailed observation.
Is this petitjeanite?
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 petitjeanite with a known reference. Petitjeanite sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to adamantine.
- 4Match the color rangeCompare against the expected color range: brown, deep yellow, white, black.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy to prismatic crystals.
Often confused with
Petitjeanite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous to adamantine on Petitjeanite and resinous to adamantine on Atelestite.
How to tell apart: Streak differs, so Petitjeanite leaves white, Mixite leaves pale bluish green.
How to tell apart: Luster reads vitreous to adamantine on Petitjeanite and subadamantine to adamantine on Preisingerite.
Often found alongside petitjeanite
Minerals reported to co-occur with petitjeanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₃O(OH)(PO₄)₂
- Mohs hardness
- 4.5
- Density
- 6.99 g/cm³
- Streak
- White
- Luster
- Vitreous to adamantine
- Transparency
- Transparent to translucent in thin fragments
- Crystal system
- Triclinic
- Crystal habit
- Platy to prismatic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in a silicified barite vein (Gadernheim, Germany)
Where rockhounds find petitjeanite
Classic worldwide localities
- Gadernheim, and on the Hohenstein, near Reichenbach, Hesse, Germany
- Pucher shaft, Schneeberg, Saxony, Germany
- Smrkovec, Slavkovský Les Mountains, about 10 km north-northeast of Mariánské Lázně (Marienbad), Czech Republic
Field-hunting tip
Where it forms: A rare secondary mineral in a silicified barite vein (Gadernheim, Germany). If you start seeing bismutite, mixite, reichenbachite in float, you are in the right ground. Typical habit: platy to prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify petitjeanite?+
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What rocks look like petitjeanite?+
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Find petitjeanite on the map
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