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Villiaumite

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Villiaumite
General
CategoryHalide mineral
Formula
(repeating unit)		NaF
Strunz classification3.AA.20
Crystal systemCubic
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupFd3m
Unit cella = 4.63 Å; Z = 4
Identification
ColorCarmine-red, lavender-pink to light orange
Crystal habitCubic crystals rare, commonly granular, massive
Cleavage{001}, perfect
TenacityBrittle
Mohs scale hardness2 – 2.5
LusterVitreous
StreakWhite
DiaphaneityTransparent
Specific gravity2.79
Optical propertiesIsotropic; weak anomalous anisotropism, then uniaxial (–)
Refractive indexn = 1.327–1.328
PleochroismStrong E = yellow; O = pink to deep carmine
Ultraviolet fluorescencedark red to orange and yellow fluorescence under SW and LW UV
SolubilitySoluble in water
References

Villiaumite is a rare halide mineral composed of sodium fluoride, NaF. It is very soluble in water and some specimens fluoresce under long and short wave ultraviolet light. It has a Mohs hardness of 2.5 and is usually red, pink, or orange in color. It is toxic to humans.

The red color is due to a broad absorption peaking at 512 nm. It is a result of radiation damage to the crystal.

Occurrence

Villiaumite, (field of view 7.1 x 4.7 mm), Poudrette quarry, Mont Saint-Hilaire, Quebec, Canada

It occurs in nepheline syenite intrusives and in nepheline syenite pegmatites. It occurs associated with aegirine, sodalite, nepheline, neptunite, lamprophyllite, pectolite, serandite, eudialyte, ussingite, chkalovite and zeolites. It has been reported from Minas Gerais, Brazil; Mont Saint-Hilaire, Quebec, Canada; the Ilimaussaq complex of Greenland; Lake Magadi, Kenya; Windhoek District, Namibia; the Fen Complex, Telemark, Norway; the Khibiny and Lovozero Massifs, Kola Peninsula, Russia; Porphyry Mountain, Boulder County, Colorado and Point of Rocks Mesa, Colfax County, New Mexico, US.

It was first described in 1908 for an occurrence in Los Islands, Guinea and named after the French explorer, Maxime Villiaume.

See also

References

  1. ^ Handbook of Mineralogy
  2. ^ Mindat.org
  3. Webmineral
  4. "Villiaumite Visible Spectra (350 – 1050 nm)". Archived from the original on 3 December 2013. Retrieved 29 May 2013.
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