Barroisite is a complex calcium-sodium amphibole typically found in metamorphic rocks like blueschists or amphibolites. It is difficult to distinguish from other amphiboles without specialized chemical analysis, usually appearing as dark, elongated prismatic crystals or fibrous masses.
Is this barroisite?
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 barroisite with a known reference. Barroisite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white to light gray.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, fibrous, or granular aggregates.
Often confused with
Barroisite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Barroisite leaves white to light gray, Hornblende leaves grayish-white.
How to tell apart: Streak differs, so Barroisite leaves white to light gray, Glaucophane leaves blue-gray.
Often found alongside barroisite
Minerals reported to co-occur with barroisite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- □NaCa[Mg₃Al₂](Si₇Al)O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.21 g/cm³
- Colors
- Streak
- White to light gray
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, fibrous, or granular aggregates
- Cleavage
- Perfect on {110}, intersecting at ~56° and ~124°; partings on {100}, {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In blueschist facies metamorphic rocks
Where rockhounds find barroisite
Classic worldwide localities
- Cleary Creek, 20 km north of Fairbanks, and on the northwest side of Kodiak Island, Alaska, USA
- Anglesey, near Llanfairpwllgwyngyll, Wales
- Nybö eclogite pod, Nordfjord, Norway
Field-hunting tip
Where it forms: In blueschist facies metamorphic rocks. If you start seeing omphacite, glaucophane, crossite in float, you are in the right ground. Typical habit: prismatic, fibrous, or granular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify barroisite?+
Where is barroisite found?+
What rocks look like barroisite?+
What minerals are found with barroisite?+
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Find barroisite on the map
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