Perraultite is a rare manganese-dominant silicate typically found in the miarolitic cavities of alkaline igneous rocks. It is most recognized for its distinct dark brown tabular crystal form and often occurs as an accessory mineral in complex pegmatites. Collectors primarily source this mineral from the famous Mont Saint-Hilaire locality in Canada.
Is this perraultite?
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 perraultite with a known reference. Perraultite sits at Mohs ~4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous on fresh surfaces to slightly waxy on exposed faces.
- 4Match the color rangeCompare against the expected color range: orange brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: twinning common.
Often confused with
Perraultite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Neptunite is the harder of the two (Mohs 5-6 vs. ~4); streak differs, so Perraultite leaves pale brown, Neptunite leaves cinnamon-brown.
How to tell apart: Streak differs, so Perraultite leaves pale brown, Bornemanite leaves white; luster reads vitreous on fresh surfaces to slightly waxy on exposed faces on Perraultite and pearly on Bornemanite.
Often found alongside perraultite
Minerals reported to co-occur with perraultite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaBaMn₄Ti₂(Si₂O₇)₂O₂(OH)₂F
- Mohs hardness
- ~4
- Density
- 3.71 g/cm³
- Colors
- Streak
- Pale brown
- Luster
- Vitreous on fresh surfaces to slightly waxy on exposed faces
- Transparency
- Opaque to translucent, transparent in small fragments
- Crystal system
- Monoclinic
- Crystal habit
- Twinning common
- Cleavage
- Very good on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In pegmatite dikes in nepheline syenite in an intrusive alkalic gabbro-syenite complex
Where rockhounds find perraultite
Classic worldwide localities
- Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Where it forms: In pegmatite dikes in nepheline syenite in an intrusive alkalic gabbro-syenite complex. If you start seeing kupletskite, catapleiite, microcline in float, you are in the right ground. Typical habit: twinning common. Train your eye for that shape before scanning the outcrop.
Common questions
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Find perraultite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
