Amstallite is a rare calcium aluminum silicate mineral often found as delicate, colorless to white prismatic crystals. It primarily occurs in the amphibolites near Amstall, Austria, where it forms in fissures and cavities. Collectors prize it for its rarity and its distinct crystal morphology in radial clusters.
Is this amstallite?
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 amstallite with a known reference. Amstallite 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. Amstallite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Amstallite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, radial aggregates.
Often confused with
Amstallite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside amstallite
Minerals reported to co-occur with amstallite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaAl(Si₃Al)O₈(OH)₂·H₂O
- Mohs hardness
- 4
- Density
- 2.26 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Radial Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphic Rocks, Specifically Amphibolite
- Typical price
- $50-300 per specimen
Where rockhounds find amstallite
Classic worldwide localities
- Amstall, Austria
Field-hunting tip
Look in metamorphic rocks, specifically amphibolite country — that is the host setting where amstallite typically forms. If you start seeing quartz, prehnite, titanite in float, you are in the right ground. Field specimens usually show a prismatic crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find amstallite on the map
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