Khomyakovite is an exceedingly rare mineral of the

eudialyte group Eudialyte group is a group of complex trigonal zircono- and, more rarely, titanosilicate minerals with general formula (1)N(2)N(3)N(4)N(5)sub>3 (1a)M(1b)sub>3M(2)3M(4)Z3 i24O72'4X2, where N(1) and N(2) and N(3) and N(5) = Na+ and more rarely H3 ...

, with formula .Mindat, Khomyakovite, http://www.mindat.org/min-7137.htmlJohnsen, O., Gault, R.A., Grice, J.D., and Ercit, T.S., 1999: Khomyakovite and manganokhomyakovite, two new members of the eudialyte group from Mont Saint-Hilaire, Quebec, Canada. The Canadian Mineralogist 37, 893-899 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.Johnsen, O., Ferraris, G., Gault, R.A., Grice, D.G., Kampf, A.R., and Pekov, I.V., 2003. The nomenclature of eudialyte-group minerals. The Canadian Mineralogist 41, 785-794 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 Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...

, although many other members display strontium diadochy. Khomyakovite is the third eudialyte-group mineral with essential tungsten (after johnsenite-(Ce) and manganokhomyakovite).

Occurrence and association

Khomyakovite, manganokhomyakovite, johnsenite-(Ce) and

oneillite Oneillite is a rare mineral of the eudialyte group with the chemical formula .Mindat, Oneillite, http://www.mindat.org/min-11029.htmlJohnsen, O., Grice, J.D., and Gault, R.A., 1999. Oneillite: a new Ca-deficient and ''REE''-rich member of the eud ...

are four eudialyte-group minerals with type locality in Mont Saint-Hilaire, Quebec, Canada. Khomyakovite itself is associated with analcime, annite, natrolite, titanite, calcite, and pyrite.

Notes on chemistry

Impurities in khomyakovite include

niobium Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...

, potassium and manganese, with minor rare earth elements, magnesium, titanium, hafnium and aluminium.

References

Cyclosilicates Sodium minerals Strontium minerals Calcium minerals Iron minerals Zirconium minerals Tungsten minerals Trigonal minerals Minerals in space group 160 {{silicate-mineral-stub