Pale yellow crystals of the rare mineral chlormayenite from the type locality in Eifel (Ettringer Bellerberg, Eifel, Rhineland-Palatinate, Germany). Mayenite has been redefined and renamed chlormayenite. — Photo: David Hospital · CC BY-SA 4.0
Chlormayenite
A rare cubic calcium-aluminium oxide-chloride first reported in 1964 from Germany's Eifel volcanic complex.
Intro adapted from Wikipedia (CC BY-SA).
Chlormayenite is an IMA-recognized mineral species in the halide class, with the chemical formula Ca₁₂Al₁₄O₃₂[ ₄Cl₂].
It crystallizes in the cubic crystal system (space group I-43d). It is a member of the Mayenite structural group.
Key properties: specific gravity 2.85; refractive index 1.629; optically isotropic.
IMA symbol Cmy, IMA status: approved, named in 1963.