{{Short description|Halide mineral}} {{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) <br/>H-M symbol: (4/m {{overline|3}} 2/m) | symmetry = ''F''m{{overline|3}}m (No. 225) | 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 = <ref name=Handbook>[http://rruff.geo.arizona.edu/doclib/hom/villiaumite.pdf Handbook of Mineralogy]</ref><ref name=Mindat>[http://www.mindat.org/min-4181.html Mindat.org]</ref><ref name=Webmin>[http://www.webmineral.com/data/Villiaumite.shtml Webmineral]</ref> }} '''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.<ref name=Mindat/>
The red color is due to a broad absorption peaking at 512 nm. It is a result of radiation damage to the crystal.<ref name="gp">{{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}}</ref>
==Occurrence== [[File:Villiaumite2 - Poudrette quarry, Mont Saint-Hilaire, Quebec, Canada.jpg|thumb|left|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.<ref name=Handbook/> 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.<ref name=Mindat/>
It was first described in 1908 for an occurrence in Los Islands, Guinea and named after the French explorer, Maxime Villiaume.<ref name=Mindat/> {{clear|left}}
==See also== * List of minerals
==References== {{Reflist}}
{{Commons}}
Category:Sodium minerals Category:Fluorine minerals Category:Cubic minerals Category:Minerals in space group 227 Category:Minerals described in 1908 Category:Rocksalt group