Absolutely gemmy crystal of the very rare mineral eifelite in a very small matrix. Eifelite is an extreme rarity from Eifel. In all the active collecting at Bellerberg, eifelite has only been found once. Eifelite has only been found in Eifel worldwide (Bellerberg, Ettringen, Eifel Mountains, Rhineland-Palatinate, Germany). — Photo: David Hospital · CC BY-SA 4.0
Eifelite
Eifelite is an IMA-recognized mineral species in the silicate class, with the chemical formula KNa₂(MgNa)(Mg₃Si₁₂)O₃₀.
It crystallizes in the hexagonal crystal system (space group P6/mcc). It is a member of the Milarite structural group.
Key properties: specific gravity 2.67; White streak; Vitreous luster; optically uniaxial.
IMA symbol Eif, IMA status: approved, named in 1980.
Found in vesicles in contact metamorphosed basement gneiss xenoliths in leucite tephrite.
It is found associated with Tridymite, hematite, pseudobrookite, pyroxene, amphibole, quartz, sanidine.
The name is derived from the locality in the Eifel district, Rhineland-Palatinate, Germany.