Villiaumite

(repeating unit)NaFStrunz classification3.AA.20Crystal systemCubicCrystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)Space groupFd3mUnit cella = 4.63 Å; Z = 4IdentificationColorCarmine-red, lavender-pink to light orangeCrystal habitCubic crystals rare, commonly granular, massiveCleavage{001}, perfectTenacityBrittleMohs scale hardness2 – 2.5LusterVitreousStreakWhiteDiaphaneityTransparentSpecific gravity2.79Optical propertiesIsotropic; weak anomalous anisotropism, then uniaxial (–)Refractive indexn = 1.327–1.328PleochroismStrong E = yellow; O = pink to deep carmineUltraviolet fluorescencedark red to orange and yellow fluorescence under SW and LW UVSolubilitySoluble in waterReferences[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. ^ a b Handbook of Mineralogy
  2. ^ a b c d 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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