Rosenbergite is a rare aluminum fluoride hydrate mineral primarily found as a sublimation product in fumaroles. It typically occurs as small, colorless to white prismatic crystals and is noted for its relative softness and specific formation environment.
Is this rosenbergite?
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 rosenbergite with a known reference. Rosenbergite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Rosenbergite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Rosenbergite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: prismatic crystals.
Often confused with
Rosenbergite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside rosenbergite
Minerals reported to co-occur with rosenbergite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AlF₃·3H₂O
- Mohs hardness
- 3
- Density
- 2.71 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Prismatic Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Fumaroles
- Typical price
- $50-300 per specimen
Where rockhounds find rosenbergite
Classic worldwide localities
- Vulcano, Lipari Islands, Italy
Field-hunting tip
Look in fumaroles country, the host setting where rosenbergite typically forms. If you start seeing aluminite, gypsum, sulfur in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find rosenbergite on the map
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