Taseqite
Taseqite is a rare mineral of the eudialyte group, with formula Na12Sr3Ca6Fe3Zr3NbSiO(Si9O27)2(Si3O9)2(O,OH,H2O)3Cl2. The formula given is derived from the original one and shows a separate silicon at the M4 site, basing on the nomenclature of the eudialyte group. Taseqite, khomyakovite and manganokhomyakovite are three group representatives with species-defining strontium, although many other members display stronium diadochy. Both stronium (Sr) and niobium (Nb) are essential in the crystal structure of taseqite. When compared to khomyakovite, taseqite differs in niobium- and chlorine-dominance.