Villiaumite
Villiaumite is a strongly colored Halide. Its deep, carmine red color is almost unique in the gem world. Other colorful Halide gems include Fluorite and Boleite. Villiaumite is an extremely rare gem since facetable crystals are rarely found and the mineral is very soft (2.0 – 2.5), has perfect cleavage and is slightly soluble in water. Since it is a sodium salt and is water soluble, Villiaumite should be kept very dry, maybe even stored with a desiccant, to avoid moisture absorption which could destroy mineral specimens or gemstones.
Villiaumite is found in only a few locations worldwide, including Rouma Isle, Los Islands, Guinea (the Type Locality); Mts. Karnasurt and Alluaiv, Lovozero massif, and from the Khibiny massif, Kola Peninsula, Russia; Kvanefjeld, Il´imaussaq intrusion, Greenland; Aris, about 20 km south of Windhoek, Namibia; Lake Magadi, Kenya; Po¸cos de Caldas, Minas Gerais, Brazil; in the USA, at Point of Rocks, Colfax County, New Mexico; on Porphyry Mountain, Jamestown district, Boulder County, Colorado; relatively large crystals from Mont Saint-Hilaire, Quebec, Canada.
Most of these sources only produce massive material not suitable for faceting. Mont Saint-Hilaire, Quebec, Canada and Khibiny massif, Kola Peninsula, Russia were about the only sources of facetable crystals and these crystals are very rare even from these locations. The most significant new find of gem quality Villiaumite crystals is from the Aris Quarries (Ariskop Quarry; Railway Quarry), Aris, Windhoek, Windhoek District, Khomas Region, Namibia.
| Category: | Halide mineral |
| Formula: | NaF |
| Sodium fluoride | |
| Crystallography: | Isometric – Hexoctahedral |
| Crystal Habit: | Crystals are rare, cubic, to 15 cm; commonly granular, massive. |
| Twinning: | None |
| Cleavage: | [100] Perfect, [010] Perfect, [001] Perfect |
| Fracture: | Irregular to Uneven |
| Tenacity: | Brittle |
| Hardness (Mohs): | 2.0 – 2.5 |
| Hardness (Vickers): | VHN200=1239 – 1467 kg/mm2 |
| Density: | 2.79 – 2.80 (g/cm3) |
| Luminescence: | Fluorescent; glows Yellow under SW UV and LW UV |
| Radioactivity: | Not Radioactive |
| Other: | Soluble in water |
| Health Warning: | CAUTION: Poisonous! Do not lick or ingest. Wash hands after handling! |
| Color: | Carmine Red, Dark Red, Pink, Lavender-Pink, Light Orange, Orangish Brown |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous (glassy) |
| Refractive Index: | 1.327 – 1.328 Isotropic; weak anomalous birefringence, then Uniaxial ( – ) |
| Birefringence: | 0.00 Isotropic (weak anomalous birefringence) |
| Dispersion: | n/a |
| Pleochroism: | Strong; E = Yellow, O = Pink to deep Red |
