What is "almarudite"

n. (context mineral English) A hexagonal-dihexagonal dipyramidal mineral containing aluminum, beryllium, calcium, iron, magnesium, manganese, oxygen, potassium, silicon, sodium, and zinc.

Almarudite is an extremely rare alkaline manganese beryllium silicate mineral of the cyclosilicates (ring silicates) class, with formula written as K([],Na)(Mn,Fe,Mg)(Be,Al)[SiO], from the volcanic environment of the Eifel Mountains, Germany.