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Faizievite

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Faizievite
General
CategorySilicate mineral, Cyclosilicate
Formula
(repeating unit)
K2Na(Ca6Na)Ti4Li6Si24O66F2
IMA symbolFai[1]
Dana classification63.2.10.1
Crystal systemTriclinic
Crystal classPinacoidal (1)
(same H-M symbol)
Space groupP1
Unit cella = 9.82, b = 9.82
c = 17.31 [Å], α = 99.209(2)°
β = 94.67(2)°, γ = 119.839(1)° (approximated); Z = 1
Identification
ColorColorless
Crystal habittabular plates
CleavageNone
TenacityBrittle
Mohs scale hardness4-4.5
LusterVitreous
DiaphaneityOpaque
Density2.83 (measured)
Optical propertiesBiaxal (+)
Refractive indexnp=1.65, nm=1.66 (approximated)
2V angle-72o (measured), -70o (calculated, approximated)
References[2][3]

Faizievite is a very rare mineral[3] with the formula K2Na(Ca6Na)Ti4Li6Si24O66F2.[2] This triclinic mineral is chemically related to baratovite and katayamalite.[4][5] Faizievite is a single-locality mineral, coming from the moraine of the Darai-Pioz glacier, Tien Shan Mountains, Tajikistan. Alkaline rocks of this site are famous for containing numerous rare minerals, often enriched in boron, caesium, lithium, titanium, rare earth elements, barium, and others.[6]

Occurrence and association

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Faizievite was detected in quartz boulders, together with aegirine, baratovite, fluorite, leucosphenite, pectolite, and polylithionite.[2]

Notes on chemistry and structure

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Strontium and trace amounts of rubidium, barium and niobium are present in the structure of faizievite. One of the sodium sites is partially vacant, and fluorine may be substituted by oxygen.[2]

Relation to other minerals

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Faizievite is related to beryl and osumilite groups of minerals.[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 d Agakhanov, A.A., Pautov, L.A., Uvarova, Y.A., Sokolova, E.V., Hawthorne, F.C., Karpenko, V.Y., and Gafurov, F.G., 2007. Faizievite, K2Na(Ca6Na)Ti4Li6Si24O66F2 - a new mineral species. New data on minerals 42, 5-10
  3. ^ a b c "Faizievite: Faizievite mineral information and data". Mindat.org. Retrieved 2016-03-05.
  4. ^ "Baratovite: Baratovite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  5. ^ "Katayamalite: Katayamalite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  6. ^ "Darai-Pioz Glacier (Dara-i-Pioz; Dara-Pioz), Alai Range (Alayskiy), Tien Shan Mtn, Region of Republican Subordination, Tajikistan - Mindat.org". Mindat.org. Retrieved 2016-03-05.