Schäferite

Schäferite
General
Category Phosphate mineral
Berzeliite group
Garnet structural group
Formula
(repeating unit)		 Ca2NaMg2[VO4]3
Strunz classification 8.AC.25
Crystal system Cubic
Crystal class Hexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space group Ia3d
Unit cell a = 12.427 Å, Z = 8
Identification
Formula mass 496.57 g/mol
Color Red, orange-red
Crystal habit Octahedral crystals
Cleavage None
Fracture Conchoidal
Mohs scale hardness 5
Luster Vitreous
Streak Yellow
Diaphaneity Transparent
Optical properties Isotropic
Refractive index n = 1.96
References [1][2]

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.[3] Schäferite is isotropic, meaning that the velocity of light is the same no matter which direction the light passes through.[2]

It was named after Helmut Schäfer (born 1931) who discovered it in a quarry on the Bellerberg Volcano in Germany.[1] It is found only in the Eifel Mountains volcanic area near Mayen, Laacher See district of Germany.[1] 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.[2]

References

  1. 1 2 3 Ralph, Jolyon and Ida Chau, 17 August 2010, "Schäferite." http://www.mindat.org/min-7279.html. Accessed 27 September 2010.
  2. 1 2 3 Barthelmy, David, 1997-2010, “Schäferite Mineral Data.” http://www.webmineral.com/data/Schaferite.shtml. Accessed 27 September 2010.
  3. ↑ Verlagsbuchhandlung, E.S. (1999) Schäferite, a new vanadium garnet. Neues Jahrbuch Fur Mineralogie,1, 123-134.


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