What is "khomyakovite"

n. (context mineralogy English) A mineral containing calcium, chlorine, hydrogen, iron, oxygen, silicon, sodium, strontium, tungsten, and zirconium.

Khomyakovite is an exceedingly rare mineral of the eudialyte group, with formula NaSrCaFeZrWSi(SiO)(SiO)O(O,OH,HO)(OH,Cl). The original formula was extended to show the presence of both the cyclic silicate groups and M4-site silicon, according to the nomenclature of the eudialyte group. Some niobium substitutes for tungsten in khomyakovite. Khomyakovite is an iron-analogue of manganokhomyakovite, the second mineral being a bit more common. The two minerals are the only group representatives, beside taseqite, with species-defining strontium, although many other members display stronium diadochy. Khomyakovite is the third eudialyte-group mineral with essential tungsten (after johnsenite-(Ce) and manganokhomyakovite).