What is Villiaumite?
Villiaumite is a vivid red sodium fluoride found in unusual alkaline rocks and valued for colour, cubic form and extreme water solubility.
Mineralogy and structure
Reference formula: NaF. Villiaumite is cubic and readily dissolves in water. COD 9007457 is an exact NaF structural reference. Red colour can fade or surfaces can be damaged when humidity is uncontrolled. Villiaumite is classified with halides and has cubic crystal symmetry. Typical hardness is 2–2.5 on the Mohs scale and specific gravity is approximately 2.8–2.9.
Colour, lustre and habit
Typical colours include red, orange-red, pink, orange, colourless. The usual cubic, granular, massive habit and vitreous, greasy lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Villiaumite forms in or is associated with nepheline-syenite complexes, alkaline pegmatites and silica-undersaturated intrusive rocks. Important documented localities include Guinea, Canada, Russia, Greenland and other rare alkaline-rock localities.
A red cube from an alkaline complex
Villiaumite is visually direct but technically demanding: the red cubic crystal is attractive precisely because its chemistry makes preservation difficult. Intact form, dryness and provenance are essential.
Collecting and care
Water-soluble and potentially hazardous: keep sealed and dry, never wash or taste, avoid skin and eye contact, and handle as a protected mineral specimen.
