Strätlingite is a rare layered double hydroxide mineral typically found as small, thin, platy crystals in contact-metamorphosed limestone. It is most recognized for its association with minerals like ettringite and portlandite in the ejecta of volcanic systems like those in the Eifel region of Germany.
Is this strätlingite?
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 strätlingite with a known reference. Strätlingite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Strätlingite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Strätlingite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, pale yellow, pale green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy crystals, pseudo-hexagonal, micaceous.
Often confused with
Strätlingite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside strätlingite
Minerals reported to co-occur with strätlingite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Al(AlSi)O₂(OH)₁₀·2.5H₂O
- Mohs hardness
- 2
- Density
- 2.12 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Platy Crystals, Pseudo-hexagonal, Micaceous
- Cleavage
- Perfect On {0001}
- Rarity
- Rare
- Uses
- Scientific Research, Collector
- Host rock
- Metamorphosed Limestone Inclusions in Volcanic Rocks (sanidinite Facies)
- Typical price
- $20-150 thumbnail
Where rockhounds find strätlingite
Classic worldwide localities
- Ettringen, Germany
- Mont Saint-Hilaire, Canada
- Khibiny Massif, Russia
Field-hunting tip
Look in metamorphosed limestone inclusions in volcanic rocks (sanidinite facies) country — that is the host setting where strätlingite typically forms. If you start seeing ettringite, portlandite, tobermorite in float, you are in the right ground. Field specimens usually show a platy crystals, pseudo-hexagonal, micaceous habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find strätlingite on the map
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