Strätlingite - Germany, Rhineland-Palatinate, Eifel, Ettringen, Bellerberg, Caspar Quarry - 1,5 mm Photos from tomeikminerals.com can be used under a Creative Commons Licenese 4.0 CC-BY, as explained in: https://www.tomeikminerals.com/about-me . — Photo: Henk Smeets - Tomeik Minerals · CC BY 4.0
Strätlingite
Strätlingite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₂Al(Si,Al)₂O₂(OH)₁₀·2.25H₂O.
It crystallizes in the hexagonal crystal system (space group R-3m).
Key properties: optically uniaxial.
IMA symbol Srä, IMA status: approved, named in 1975.
Found in a metamorphosed limestone xenolith in basalt (Bellerberg volcano, Germany); within metamorphosed clay xenoliths in phonolite (Montalto di Castro, Italy).
It is found associated with Nepheline, melilite, garnet, thomsonite, gismondine, ettringite, hydrocalumite (Bellerberg volcano, Germany); tobermorite, ettringite, calcite.
The name refers to W. StrÄa tling, who synthesized the mineral.