Golyshevite is a rare mineral of the eudialyte group,[2] with the formula Na10Ca3Ca6Zr3Fe2SiNb(Si3O9)2(Si9O27)2CO3(OH)3•H2O.[3] 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.[4] The characteristic feature of golyshevite is calcium-rich composition, with calcium at two main sites instead of one site.[3] Together with feklichevite, fengchengite, ikranite and mogovidite it is a ferric-iron-dominant representative of the group.[2] It is chemically similar to mogovidite.[2][3] Golyshevite was named after Russian crystallographer Vladimir Mikhailovich Golyshev.[3]
Golyshevite | |
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General | |
Category | Silicate mineral, cyclosilicate |
Formula (repeating unit) | (Na,Ca)10Ca9(Fe3+,Fe2+)2Zr3NbSi25O72(CO3)(OH)3·H2O (original form) |
IMA symbol | Gsv[1] |
Strunz classification | 9.CO.10 |
Dana classification | 64.1.6 |
Crystal system | Trigonal |
Crystal class | Ditrigonal pyramidal (3m) (same H-M symbol) |
Space group | R3m |
Unit cell | a = 14.23 c = 29.98 [Å] (approximated); Z = 3 |
Identification | |
Color | Brown to reddish-brown |
Crystal habit | Grains and crystals |
Cleavage | No |
Tenacity | Brittle |
Specific gravity | 2.89 (measured) |
Optical properties | Uniaxial (−) |
Refractive index | nω = 1.62, nε = 1.61 (approximated) |
Pleochroism | Green to pale yellow |
References | [2][3] |
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.[3]
Impurities in golyshevite include chlorine, potassium, manganese, aluminium, cerium and lanthanum.[3]
Calcium in golyshevite is present at M(1) and N(4) sites.[3]