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Ferrokentbrooksite

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Ferrokentbrooksite
Ferrokentbrooksite, Amphibole Supergroup-166795
General
CategoryCyclosilicate
Formula
(repeating unit)
Na15Ca6(Fe,Mn)3Zr3NbSi25O73(O,OH,H2O)3(Cl,F,OH)2 (original form)
IMA symbolFktb[1]
Strunz classification9.CO.10 (10 ed)
8/E.23-15 (8 ed)
Dana classification64.1.2.2
Crystal systemTrigonal
Crystal classDitrigonal pyramidal (3m)
H-M symbol: (3m)
Space groupR3m
Unit cella = 14.25, c = 30.03 [Å] (approximated); Z = 3
Identification
ColorReddish brown to red
Crystal habitPseudo-octahedra
CleavageNo
FractureUneven to conchoidal
LusterVitreous
StreakWhite
DiaphaneityTransparent
Refractive indexnω = 1.62, nε = 1.62 (approximated)
Common impuritiesREE (mainly Ce and Y), K, Sr
References[2][3]

Ferrokentbrooksite is a moderately rare mineral of the eudialyte group,[2] with formula Na15Ca6(Fe,Mn)3Zr3NbSi25O73(O,OH,H2O)3(Cl,F,OH)2.[3] The original formula was extended form to show the presence of cyclic silicate groups and presence of silicon at the M4 site, according to the nomenclature of eudialyte group.[4] As suggested by its name, it is the (ferrous) iron analogue of kentbrooksite.[3] When compared to the latter, it is also chlorine-dominant instead of being fluorine-dominant.[2] The original (holotype) material is also relatively enriched in rare earth elements, including cerium and yttrium.[3]

Occurrence and association

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Ferrokentbrooksite was discovered in Mont Saint-Hilaire, Quebec, Canada – a site wealth in rare alkaline minerals.[5] At the site ferrokentbrooksite coexists with aegirine, albite, ancylite-(Ce), calcite, catapleiite, fluorite, fluorapatite, gonnardite, microcline, natrolite, nepheline, rhodochrosite, and serandite.[3]

Notes on chemistry

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Beside fluorine, ferrokentbrooksite has admixtures of rare earth elements (including cerium, yttrium, lanthanum, neodymium and some gadolinium and samarium), potassium, strontium, and contains minor admixtures of titanium, hafnium, and tantalum.[3]

Notes on structure

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Iron in ferrokentbrooksite has coordination number 5.[3]

References

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  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. ^ a b c Mindat, Ferrokentbrooksite, http://www.mindat.org/min-7106.html
  3. ^ a b c d e f g Johnsen, O., Grice, J.D., and Gault, R.A., 2003: Ferrokentbrooksite, a new member of the eudialyte group from Mont Saint-Hilaire, Quebec, Canada. The Canadian Mineralogist 41(1), 55–60
  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. ^ "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. Retrieved 2016-03-11.