Fluoborite

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Fluoborite
General
Category Borate mineral
Strunz classification 06.AB.50
Crystal symmetry Hexagonal dipyramidal
H-M symbol: (6/m)
Space group: P 63/m
Unit cell a = 8.8612 Å, c = 3.1021 Å; Z=3
Identification
Formula mass 186.61 g
Color Colorless to violet or white
Crystal habit Acicular, prismatic, stellate
Crystal system Hexagonal
Cleavage Good on {0001}
Mohs scale hardness 3.5
Luster Vitreous to silky
Streak white
Diaphaneity Translucent to transparent
Specific gravity 2.98
Optical properties Uniaxial (-)
Refractive index nω = 1.570 nε = 1.534
Birefringence 0.036
Ultraviolet fluorescence Intense cream-white under SW UV
References [1][2][3]

Fluoborite has a chemical formula of Mg3(BO3)(F,OH)3. Its name comes from its main chemical components, FLUOrine and BORon. It was first described in 1926.[2]

Fluoborite's crystal system is hexagonal, meaning it has one six-fold axis of rotation. It also has a mirror plane perpendicular to the c-axis.[4] Fluoborite is uniaxial, just like all other hexagonal minerals. Uniaxial means it has only one optic axis. It is anisotropic. Its relief is low, and it is birefringent.

There are three major settings fluoborite is found. It is found in skarns developed in metamorphosed boron-rich magnesium rocks, contact metamorphosed marble, and in contact metasomatic magnetite deposits. There are two major type localities for fluoborite. One is Tall Mine, Kallmora, Norberg, Västmanland, Sweden. It is an iron mine in a contact metasomatic magnetite deposit. The other type locality is the Huerta del Vinagre mine, Spain.[5]

It occurs associated with ludwigite, chondrodite, magnetite and calcite in the Tallgruvan, Sweden occurrence. It occurs with mooreite, willemite, fluorite, hydrozincite, pyrochroite, zincite and rhodochrosite at Sterling Hill, New Jersey.[1]

References[edit]

  1. ^ a b Handbook of Mineralogy
  2. ^ a b Fluoborite on Mindat.org
  3. ^ Fluoborite Mineral Data on Webmineral
  4. ^ Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (2003)Fluoborite. Handbook of Mineralogy Volume V Borates, Carbonates, Sulfates, 791 p. Mineral Data Publishing, Tucson, AZ.
  5. ^ Camara, F. and Ottolini, L., 2000. "New data on the crystal-chemistry of fluoborite by means of SREF, SIMS, and EMP analysis." http://rruff.geo.arizona.edu/doclib/am/vol85/AM85_103.pdf. Accessed 1 November 2010.