Villiaumite
{{infobox mineral
|boxtextcolor=|boxbgcolor=#c55e35| name = Villiaumite
| category = Halide mineral
| image = Villiaumite-t5128a.jpg
| imagesize = 260px
| alt =
| caption =
| formula = NaF
| molweight =
| strunz = 3.AA.20
| dana =
| system = Cubic
| class = Hexoctahedral (m{{overline|3}}m)
H-M symbol: (4/m {{overline|3}} 2/m)
| symmetry = Fd{{overline|3}}m
| unit cell = a = 4.63 Å; Z = 4
| color = Carmine-red, lavender-pink to light orange
| colour =
| habit = Cubic crystals rare, commonly granular, massive
| twinning =
| cleavage = {001}, perfect
| fracture =
| tenacity = Brittle
| mohs = 2 – 2.5
| luster = Vitreous
| streak = White
| diaphaneity = Transparent
| gravity = 2.79
| density =
| polish =
| opticalprop = Isotropic; weak anomalous anisotropism, then uniaxial (–)
| refractive = n = 1.327–1.328
| birefringence =
| pleochroism = Strong E = yellow; O = pink to deep carmine
| 2V =
| dispersion =
| extinction =
| length fast/slow =
| fluorescence= dark red to orange and yellow fluorescence under SW and LW UV
| absorption =
| melt =
| fusibility =
| diagnostic =
| solubility = Soluble in water
| other =
| alteration =
| references = [http://rruff.geo.arizona.edu/doclib/hom/villiaumite.pdf Handbook of Mineralogy][http://www.mindat.org/min-4181.html Mindat.org][http://www.webmineral.com/data/Villiaumite.shtml Webmineral]
}}
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.{{cite web|url=http://minerals.gps.caltech.edu/files/visible/villiaumite/index.htm|title=Villiaumite Visible Spectra (350 – 1050 nm)|access-date=29 May 2013|archive-url=https://web.archive.org/web/20131203033233/http://minerals.gps.caltech.edu/FILES/Visible/villiaumite/index.htm|archive-date=3 December 2013|url-status=dead|df=dmy-all}}
Occurrence
File:Villiaumite2 - Poudrette quarry, Mont Saint-Hilaire, Quebec, Canada.jpg, 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.
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