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Golyshevite

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Rare cyclosilicate mineral
Golyshevite
Golyshevite crystals in matrix, some of them showing a pseudohexagonal section, with the typical yellowish-brown zircon-like colour. Locality: Kovdor Phlogopite Mine, Kovdor Massif, Northern Region, Russian Federation Size: 2.3 × 2.1 × 1.5 cm
General
CategorySilicate mineral, cyclosilicate
Formula
(repeating unit)		(Na,Ca)10Ca9(Fe,Fe)2Zr3NbSi25O72(CO3)(OH)3·H2O (original form)
IMA symbolGsv
Strunz classification9.CO.10
Dana classification64.1.6
Crystal systemTrigonal
Crystal classDitrigonal pyramidal (3m)
(same H-M symbol)
Space groupR3m
Unit cella = 14.23
c = 29.98  (approximated); Z = 3
Identification
ColorBrown to reddish-brown
Crystal habitGrains and crystals
CleavageNo
TenacityBrittle
Specific gravity2.89 (measured)
Optical propertiesUniaxial (−)
Refractive indexnω = 1.62, nε = 1.61 (approximated)
PleochroismGreen to pale yellow
References

Golyshevite is a rare mineral of the eudialyte group, with the formula Na10Ca3Ca6Zr3Fe2SiNb(Si3O9)2(Si9O27)2CO3(OH)3•H2O. The original formula was extended to show both the presence of cyclic silicate groups and silicon at the M4 site, according to the nomenclature of the eudialyte group. The characteristic feature of golyshevite is calcium-rich composition, with calcium at two main sites instead of one site. Together with feklichevite, fengchengite, ikranite and mogovidite it is a ferric-iron-dominant representative of the group. It is chemically similar to mogovidite. Golyshevite was named after Russian crystallographer Vladimir Mikhailovich Golyshev.

Occurrence and association

Golyshevite and mogovidite were found in calcium-bearing peralkaline pegmatites of the Kovdor massif, Kola Peninsula, Russia. Minerals associated with golyshevite are aegirine-augite, calcite, cancrinite, hedenbergite, orthoclase, pectolite, tacharanite, and thomsonite-Ca.

Notes on chemistry

Impurities in golyshevite include chlorine, potassium, manganese, aluminium, cerium and lanthanum.

Notes on crystal structure

Calcium in golyshevite is present at M(1) and N(4) sites.

References

  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Mindat, Golyshevite, http://www.mindat.org/min-27418.html
  3. ^ Chukanov, N.V., Moiseyev, M.M., Rastsvetayeva, R.K., Rozenberg, K.A., and Zadov, A.E., 2005. Golyshevite (Na,Ca)10Ca9(Fe,Fe)2Zr3NbSi25O72(CO3)(OH)3·H2O, and Mogovidite, Na9(Ca,Na)6Ca6(Fe,Fe)2Zr3Si25O72(CO3)(OH,H2O)4, new eudialyte-group minerals from calcium-rich agpaitic pegmatites of the Kovdor massif, Kola Peninsula. Zapiski Rossiyskogo Mineralogicheskogo Obshchestva 134(6), 36-47 (in Russian, with English abstract)
  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
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