Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
Villiaumite is seldom discussed among collectors of rare gemstones because until recently no facetable material was known. The material from Los was reported in 1976 and has been cut into tiny gemstones of deep red color. Despite their small size, they are desirable because so few stones exist. The material from Quebec is larger but very scarce. Villiaumite is somewhat water-soluble, and cutters must use special tricks (such as using alcohol as a cutting coolant) to facet the material.
Villiaumite Value
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
Villiaumite Information
| Data | Value |
| Name | Villiaumite |
| Crystallography | Isometric; crystals tiny; usually massive, granular. |
| Colors | Deep carmine-red, lavender pink to light orange; becomes colorless if heated to 300°C. |
| Luster | Vitreous. |
| Hardness | 2-2.5. |
| Density | 2.79. |
| Birefringence | Sometimes anomalous. |
| Cleavage | Perfect 1 direction; brittle. |
| Stone Sizes | Los material might yield faceted gems up to 1-2 carats. Gems under 2 carats have been cut from Quebec material. Smithsonian Institution (Washington, D.C): 1.2 (orange—red). Private Collection: 12.1 (red, Quebec, cabochon?). |
| Luminescence | None. |
| Spectral | Not diagnostic. |
| Formula | NaF |
| Pleochroism | Anomalous, strong: yellow/ pink to deep carmine-red. |
Optics: N: 1.327: isotropic.
Occurrence: In alkalic rocks, such as nepheline syenites.
Kola Peninsula, USSR.
Los, Guinea: Los is an island off the Guinea coast; facetable villiaumite occurs in nepheline syenite in reddish crystals, R.l. I l.33O—1.332, S.G. 2.79.
Francon Quarry, Mt. Ste. Hilaire, Quebec.
Comments: Villiaumite is seldom discussed among collectors of rare gemstones because until recently no facetable material was known. The material from Los was reported in 1976 and has been cut into tiny gemstones of deep red color. Despite their small size, they are desirable because so few stones exist. The material from Quebec is larger but very scarce. Villiaumite is somewhat water-soluble, and cutters must use special tricks (such as using alcohol as a cutting coolant) to facet the material.
Name: After M. Villiaume, a French explorer in whose collection of rocks from Guinea the material was first discovered.
