Manganokhomyakovite Explained

Manganokhomyakovite
Category:Cyclosilicates
Formula: (original form)
Imasymbol:Mkmy[1]
Strunz:9.CO.10 (10 ed)
8/E.23-35 (8 ed)
Dana:64.1.2.6
Class:Ditrigonal pyramidal (3m)
(same H-M symbol)
Symmetry:R3m
Unit Cell:a = 14.28, c = 30.12 [Å] (approximated); Z = 3
Color:Orange to orange-red
Habit:Pseudo-octahedra
Cleavage:None
Fracture:Uneven
Tenacity:Brittle
Mohs:5–6
Luster:Vitreous
Streak:White
Diaphaneity:Transparent to translucent
Density:3.13 (measured), 3.17 (calculated)
Opticalprop:Uniaxial (−)
Refractive:nω = 1.63, nε = 1.63 (approximated)
Pleochroism:None

Manganokhomyakovite is a very rare mineral of the eudialyte group,[2] with the chemical formula .[3] This formula is in extended form (based on the original one), to show the presence of cyclic silicate groups and domination of silicon at the M4 site, basing on the nomenclature of the eudialyte group.[4] Some niobium substitutes for tungsten in khomyakovite. As suggested by its name, manganokhomyakovite is a manganese-analogue of khomyakovite, the latter being more rare. The two minerals are the only group representatives, beside taseqite, with species-defining strontium, although many other members display strontium diadochy. Manganokhomyakovite is the third eudialyte-group mineral with essential tungsten (after johnsenite-(Ce) and khomyakovite).

Occurrence and association

Manganokhomyakovite, khomyakovite, johnsenite-(Ce) and oneillite are four eudialyte-group minerals discovered in alkaline rocks of Mont Saint-Hilaire, Quebec, Canada.[5] Association of manganokhomyakovite is rich and includes: aegirine, albite, analcime, annite, kupletskite, microcline, natrolite, sodalite, titanite, wöhlerite, zircon, cerussite, galena, molybdenite, pyrite, pyrrhotite, and sphalerite.

Notes on chemistry

Impurities in manganokhomyakovite include niobium and iron, with traces of rare earth elements, hafnium, titanium, tantalum, and aluminium.

Notes and References

  1. Warr. L.N.. 2021. IMA–CNMNC approved mineral symbols. Mineralogical Magazine. 85. 3. 291–320. 10.1180/mgm.2021.43. 2021MinM...85..291W. 235729616. free.
  2. Mindat, Manganokhomyakovite, http://www.mindat.org/min-7137.html
  3. Johnsen, 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
  4. 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
  5. Web site: Poudrette quarry (Demix quarry; Uni-Mix quarry; Desourdy quarry; Carrière Mont Saint-Hilaire), Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada - Mindat.org . Mindat.org . 2016-03-11.