What is "raslakite"

n. (context mineralogy English) A trigonal-ditrigonal pyramidal brownish red mineral containing calcium, chlorine, hydrogen, iron, niobium, oxygen, silicon, sodium, and zirconium.

Raslakite is a rare mineral of the eudialyte group with the formula NaCaFe(Na,Zr)Zr(Si,Nb)SiO(SiO)(SiO)(OH,HO)(Cl,OH). This formula is based on the original one, and is extended to show the presence of cyclic silicate groups. The additional silicon and oxygen shown in separation from the cyclic groups (in parentheses) are in fact connected with two 9-fold rings. The mineral has lowered symmetry (space group R3, instead of more specific for the group R3m one), similarly to some other eudialyte-group members: aqualite, labyrinthite, oneillite and voronkovite. The specific feature of raslakite is, among others, the presence of sodium and zirconium at the M2 site. Raslakite was named after Raslak Cirques located nearby the type locality.