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[1][2][3]

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.[2]

The red color is due to a broad absorption peaking at 512 nm. It is a result of radiation damage to the crystal.[4]

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.[1] 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.[2]

It was first described in 1908 for an occurrence in Los Islands, Guinea and named after the French explorer, Maxime Villiaume.[2]

See also

References

  1. 1 2 Handbook of Mineralogy
  2. 1 2 3 4 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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