Greenish crystal aggregates of jasmundite associated to mayenite from the famous Bellerberg (Bellerberg, Ettringen, Eifel Mountains, Rhineland-Palatinate, Germany). — Photo: David Hospital · CC BY-SA 4.0
Jasmundite
Jasmundite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₁₁O₂(SiO₄)₄S.
It crystallizes in the tetragonal crystal system (space group I4/mmm).
Key properties: Mohs hardness 5; specific gravity 3.03; White streak; Resinous luster; optically uniaxial.
IMA symbol Jas, IMA status: approved, named in 1981.
Found in metamorphosed limestone inclusions in basalt.
It is found associated with Mayenite, brownmillerite, larnite, portlandite, ettringite, calcite, vaterite, tobermorite, thaumasite.
The mineral was named to honor Professor Karl Jasmund, retired Director of the Mineralogical-Petrographic Institute, University of Cologne, Cologne, Germany.