Faizievite

Faizievite
General
Category Silicate mineral, Cyclosilicate
Formula
(repeating unit)		 K2Na(Ca6Na)Ti4Li6Si24O66F2
Dana classification 63.2.10.1
Crystal system Triclinic
Crystal class Pinacoidal (1)
(same H-M symbol)
Space group P1
Unit cell a = 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
Color Colorless
Crystal habit tabular plates
Cleavage None
Tenacity Brittle
Mohs scale hardness 4-4.5
Luster Vitreous
Diaphaneity Opaque
Density 2.83 (measured)
Optical properties Biaxal (+)
Refractive index np=1.65, nm=1.66 (approximated)
2V angle -72o (measured), -70o (calculated, approximated)
References [1][2]

Faizievite is a very rare mineral[2] with the formula K2Na(Ca6Na)Ti4Li6Si24O66F2.[1] This triclinic mineral is chemically related to baratovite and katayamalite.[3][4] 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.[5]

Occurrence and association

Faizievite was detected in quartz boulders, together with aegirine, baratovite, fluorite, leucosphenite, pectolite, and polylithionite.[1]

Notes on chemistry and structure

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.[1]

Relation to other minerals

Faizievite is related to beryl and osumilite groups of minerals.[2]

References

  1. 1 2 3 4 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
  2. 1 2 3 "Faizievite: Faizievite mineral information and data". Mindat.org. Retrieved 2016-03-05.
  3. ↑ "Baratovite: Baratovite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  4. ↑ "Katayamalite: Katayamalite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  5. ↑ "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.
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