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Schäferite

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Schäferite
General
CategoryPhosphate mineral
Berzeliite group
Garnet structural group
Formula
(repeating unit)
Ca2NaMg2[VO4]3
IMA symbolSfr[1]
Strunz classification8.AC.25
Crystal systemCubic
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupIa3d
Unit cella = 12.427 Å, Z = 8
Identification
Formula mass496.57 g/mol
ColorRed, orange-red
Crystal habitOctahedral crystals
CleavageNone
FractureConchoidal
Mohs scale hardness5
LusterVitreous
StreakYellow
DiaphaneityTransparent
Optical propertiesIsotropic
Refractive indexn = 1.96
References[2][3]

Schäferite is a rare vanadate mineral with chemical formula Ca2NaMg2[VO4]3. Schäferite is isometric, which means that it has three axes of equal length and 90° angles between the axes.[4] Schäferite is isotropic, meaning that the velocity of light is the same no matter which direction the light passes through.[3]

It was named after Helmut Schäfer (born 1931) who discovered it in a quarry on the Bellerberg Volcano in Germany.[2] It is found only in the Eifel Mountains volcanic area near Mayen, Laacher See district of Germany.[2] It occurs within a xenolith in a leucite tephrite. It is the magnesium analogue of palenzonaite and is a member of the garnet structural group.[3]

References

[edit]
  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 Ralph, Jolyon and Ida Chau, 17 August 2010, "Schäferite." http://www.mindat.org/min-7279.html. Accessed 27 September 2010.
  3. ^ a b c Barthelmy, David, 1997-2010, “Schäferite Mineral Data.” http://www.webmineral.com/data/Schaferite.shtml. Accessed 27 September 2010.
  4. ^ Verlagsbuchhandlung, E.S. (1999) Schäferite, a new vanadium garnet. Neues Jahrbuch für Mineralogie,1, 123-134.