Ferrokentbrooksite

Ferrokentbrooksite
Ferrokentbrooksite
	Ferrokentbrooksite, Amphibole Supergroup-166795
General
Category	Cyclosilicate
Formula; (repeating unit)	Na15Ca6(Fe,Mn)3Zr3NbSi25O73(O,OH,H2O)3(Cl,F,OH)2 (original form)
IMA symbol	Fktb[1]
Strunz classification	9.CO.10 (10 ed) ; 8/E.23-15 (8 ed)
Dana classification	64.1.2.2
Crystal system	Trigonal
Crystal class	Ditrigonal pyramidal (3m) ; H-M symbol: (3m)
Space group	R3m
Unit cell	a = 14.25, c = 30.03 [Å] (approximated); Z = 3
Identification
Color	Reddish brown to red
Crystal habit	pseudo-octahedra
Cleavage	No
Fracture	Uneven to conchoidal
Luster	Vitreous
Streak	White
Diaphaneity	Transparent
Refractive index	nω 1.62, nε=1.62 (approximated)
Common impurities	REE (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

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

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

Iron in ferrokentbrooksite has coordination number 5.[3]

References

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.
Mindat, Ferrokentbrooksite, http://www.mindat.org/min-7106.html
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
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
"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.

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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.

[Mindat-2] Mindat, Ferrokentbrooksite, http://www.mindat.org/min-7106.html

[CanMin-3] 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.