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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, light green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy.
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
- 1.9 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Platy
- Cleavage
- Perfect on {0001}
- Rarity
- Rare
- Uses
- Scientific research, Collector
- Host rock
- In a metamorphosed limestone xenolith in basalt (Bellerberg volcano, Germany); within metamorphosed clay xenoliths in phonolite (Montalto di Castro, Italy)
Where rockhounds find strätlingite
Classic worldwide localities
- Bellerberg volcano, two km north of Mayen, Eifel district, Germany
- A quarry at Campomorto, Montalto di Castro, Lazio, Italy
Field-hunting tip
Where it forms: In a metamorphosed limestone xenolith in basalt (Bellerberg volcano, Germany); within metamorphosed clay xenoliths in phonolite (Montalto di Castro, Italy). If you start seeing nepheline, melilite, garnet in float, you are in the right ground. Typical habit: platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify strätlingite?+
Where is strätlingite found?+
What rocks look like strätlingite?+
What minerals are found with strätlingite?+
What kind of rock does strätlingite form in?+
What is strätlingite used for?+
Find strätlingite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
