Prosopite is a rare calcium aluminum fluoride mineral typically found as a secondary alteration product in tin-bearing greisens. It most commonly appears as dull, massive, or granular masses rather than well-defined crystals, often forming as a pseudomorph after minerals like topaz or fluorite.
Is this prosopite?
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 prosopite with a known reference. Prosopite sits at Mohs 4.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Prosopite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Prosopite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray, yellowish, pinkish.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, granular, or earthy aggregates.
Often confused with
Prosopite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside prosopite
Minerals reported to co-occur with prosopite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaAl₂(F,OH)₈
- Mohs hardness
- 4.5
- Density
- 2.88 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Massive, Granular, Or Earthy Aggregates
- Cleavage
- None Observed
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins, Tin-bearing Greisens
- Typical price
- $20-100 thumbnail
Where rockhounds find prosopite
Classic worldwide localities
- Altenberg, Germany
- Geyer, Germany
- Långban, Sweden
- Lost River, Alaska, USA
- Schellerhau, Germany
Field-hunting tip
Look in hydrothermal veins, tin-bearing greisens country — that is the host setting where prosopite typically forms. If you start seeing fluorite, quartz, topaz in float, you are in the right ground. Field specimens usually show a massive, granular, or earthy aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify prosopite?+
Where is prosopite found?+
How much is prosopite worth?+
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Find prosopite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
