Rosenhahnite is a rare calcium silicate mineral typically found as platy or fibrous aggregates in metamorphic environments. It is most famous from its type locality in Mendocino County, California, where it occurs within metasomatized blocks. Collectors look for its characteristic clear to pale pink appearance and distinct cleavage, often embedded in calcite or aragonite matrices.
Is this rosenhahnite?
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 rosenhahnite with a known reference. Rosenhahnite sits at Mohs 5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Rosenhahnite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Rosenhahnite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, pale pink.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy crystals, fibrous, massive.
Often confused with
Rosenhahnite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside rosenhahnite
Minerals reported to co-occur with rosenhahnite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃Si₃O₈(OH)₂
- Mohs hardness
- 5
- Density
- 2.88 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Platy Crystals, Fibrous, Massive
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metasomatized Sedimentary Rocks, Glaucophane Schist Facies
- Typical price
- $20-150 for small specimens
Where rockhounds find rosenhahnite
Classic worldwide localities
- Russian River, California, USA
- Mendocino County, California, USA
Field-hunting tip
Look in metasomatized sedimentary rocks, glaucophane schist facies country — that is the host setting where rosenhahnite typically forms. If you start seeing calcite, aragonite, tobermorite in float, you are in the right ground. Field specimens usually show a platy crystals, fibrous, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify rosenhahnite?+
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How much is rosenhahnite worth?+
What rocks look like rosenhahnite?+
What minerals are found with rosenhahnite?+
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Find rosenhahnite on the map
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