Almarudite
An extremely rare alkaline ring-silicate containing beryllium and manganese, from the volcanic Eifel district of Germany.
Intro adapted from Wikipedia (CC BY-SA).
Almarudite is an IMA-recognized mineral species in the silicate class, with the chemical formula K( ,Na)₂(Mn,Fe,Mg)₂[(Be,Al)₃Si₁₂]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 2.72; Light orange streak; Vitreous luster; optically uniaxial.
IMA symbol Alr, IMA status: approved, named in 2002.
Found in metasomatized silica-rich xenoliths in leucite tephrite lava.
It is found associated with Tridymite, sanidine, a clinopyroxene, an amphibole, quartz, hematite, braunite (Bellerberg volcano, Germany).
The mineral was named to honor the authors’ hosting and supporting institution, “Universität Wien”, derived from the university’s proper name “ALma MAter RUDolphina”.