Khomyakovite

Khomyakovite is an exceedingly rare mineral of the eudialyte group, with formula Na12Sr3Ca6Fe3Zr3WSi(Si9O27)2(Si3O9)2O(O,OH,H2O)3(OH,Cl)2. It is a mineral containing calcium, chlorine, hydrogen, iron, oxygen, silicon, sodium, strontium, tungsten, and zirconium. 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.

General Information

  • Category: Silicate mineral, Cyclosilicate
  • Formula: Na12Sr3Ca6Fe3Zr3WSi(Si9O27)2(Si3O9)2O(O,OH,H2O)3(OH,Cl)2
  • Crystal system: Trigonal
  • Crystal class: Ditrigonal pyramidal (3m)

Properties

Khomyakovite is an iron-analogue of manganokhomyakovite, the second mineral being a bit more common. The two minerals are the only group representatives, besides taseqite, with species-defining strontium, although many other members display stronium diadochy. Khomyakovite is the third eudialyte-group mineral with essential tungsten.

  • Color: Orange to orange-red
  • Crystal habit: aggregates (anhedral to subhedral)
  • Fracture: Uneven
  • Tenacity: Brittle
  • Mohs scale hardness: 5-6
  • Luster: Vitreous
  • Streak: White
  • Diaphaneity: Transparent to translucent
  • Density: 3.14 (calculated)

Occurrence and association

Khomyakovite, manganokhomyakovite, johnsenite-(Ce) and oneillite 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.

 

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