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 4.5-5, 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: colorless, beige white.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular.
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
- 4.5-5
- Density
- 2.89 g/cm³
- Colors
- ColorlessBeige white
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Tabular
- Cleavage
- Perfect on {001}, good on {100} and {010}
- Fluorescence
- Yellowish green under SW UV; light orangish pink under LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In veins in brecciated, fine-grained, garnet- and diopside-bearing metasediments (Russian River, California, USA)
Where rockhounds find rosenhahnite
Classic worldwide localities
- Russian River, in Mendocino Co., about eight km north of Cloverdale, California, and in the Durham quarry, near Durham, Wake Co., North Carolina, USA
- Engyouji, Kochi Prefecture, Japan
- Wairere, south of Te Kuiti, New Zealand
- Staré Ransko, Czech Republic
- Asbest, Ural Mountains, Russia
Field-hunting tip
Where it forms: In veins in brecciated, fine-grained, garnet- and diopside-bearing metasediments (Russian River, California, USA). If you start seeing pectolite, xonotlite, datolite in float, you are in the right ground. Typical habit: tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify rosenhahnite?+
Where is rosenhahnite found?+
What rocks look like rosenhahnite?+
What minerals are found with rosenhahnite?+
What kind of rock does rosenhahnite form in?+
What is rosenhahnite used for?+
Find rosenhahnite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
