Villiaumite Locality: Aris Quarries (Ariskop Quarry; Railway Quarry), Aris, Windhoek District, Khomas Region, Namibia FOV 2.8 x 2.0 mm Thanks to Vic Cloete (200 — Photo: Modris Baum · Public domain
Villiaumite
Sodium fluoride — a rare water-soluble red-to-orange halide of alkaline intrusions.
Intro adapted from Wikipedia (CC BY-SA).
Villiaumite is an IMA-recognized mineral species in the halide class, with the chemical formula NaF.
It crystallizes in the cubic crystal system (space group Fm3m). It is a member of the Rocksalt structural group.
Key properties: Mohs hardness 2–2.5; specific gravity 2.79; typically red; White streak; Vitreous luster; refractive index 1.328; optically isotropic.
IMA symbol Vll, grandfathered status — known before the IMA’s founding, named in 1908.
Found in nepheline syenite and nepheline syenite pegmatites; in lake-bed deposits.
It is found associated with Aegirine, sodalite, nepheline, neptunite, lamprophyllite, pectolite, serandite, eudialyte, ussingite, chkalovite, zeolites.
The mineral was named to honor Maxime Villiaume, French explorer, in whose collections of rocks from Guinea the mineral was first found.
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