Trolleite is a rare phosphate mineral often found in high-pressure metamorphic environments. It typically appears as pale blue-green or white massive aggregates, frequently associated with other aluminum phosphates like lazulite and augelite.
Is this trolleite?
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 trolleite with a known reference. Trolleite sits at Mohs 8.5, 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.
- 4Match the color rangeCompare against the expected color range: light blue, light green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, granular, rarely as small pseudo-hexagonal crystals.
Often confused with
Trolleite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Trolleite is noticeably harder (Mohs 8.5 vs. 5.5-6).
How to tell apart: Trolleite is noticeably harder (Mohs 8.5 vs. 6).
How to tell apart: Trolleite is noticeably harder (Mohs 8.5 vs. 4.5).
Often found alongside trolleite
Minerals reported to co-occur with trolleite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₄(PO₄)₃(OH)₃
- Mohs hardness
- 8.5
- Density
- 3.10 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Massive, granular, rarely as small pseudo-hexagonal crystals
- Cleavage
- In two directions, indistinct
- Rarity
- Rare
- Uses
- Collector, Lapidary
- Host rock
- In amphibolite-grade metamorphic rocks
Where rockhounds find trolleite
Classic worldwide localities
- Kyanite Corporation mine on Willis Mountain, Buckingham Co., Virginia, USA
- Four km west of Glendevey, Larimer Co., Colorado, USA
- Champion mine, White Mountains, Mono Co., California, USA
- Västanå mine, near Näsum, Skåne, Sweden
- Hålsjöberg, Värmland, Sweden
- Hökensås, Västergötland, Sweden
Field-hunting tip
Where it forms: In amphibolite-grade metamorphic rocks. If you start seeing berlinite, attakolite, augelite in float, you are in the right ground. Typical habit: massive, granular, rarely as small pseudo-hexagonal crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify trolleite?+
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What rocks look like trolleite?+
What minerals are found with trolleite?+
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Find trolleite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
