| Villiaumite | |
|---|---|
|   | |
| General | |
| Category | Halide mineral | 
| Formula | NaF | 
| Strunz classification | 3.AA.20 | 
| Crystal system | Cubic | 
| Crystal class | Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m) | 
| Space group | Fd3m | 
| Unit cell | a = 4.63 Å; Z = 4 | 
| Identification | |
| Color | Carmine-red, lavender-pink to light orange | 
| Crystal habit | Cubic crystals rare, commonly granular, massive | 
| Cleavage | {001}, perfect | 
| Tenacity | Brittle | 
| Mohs scale hardness | 2 – 2.5 | 
| Luster | Vitreous | 
| Streak | White | 
| Diaphaneity | Transparent | 
| Specific gravity | 2.79 | 
| Optical properties | Isotropic; weak anomalous anisotropism, then uniaxial (–) | 
| Refractive index | n = 1.327–1.328 | 
| Pleochroism | Strong E = yellow; O = pink to deep carmine | 
| Ultraviolet fluorescence | dark red to orange and yellow fluorescence under SW and LW UV | 
| Solubility | Soluble in water | 
| References | [1] [2] [3] | 
Villiaumite is a rare halide mineral composed of sodium fluoride, Na F. 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]
 
 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]