Sellaite

Sellaite is a magnesium fluoride mineral with formula: MgF₂. It crystallizes in the tetragonal crystal system typically as clear to white vitreous prisms. It may be fibrous and occur as radiating aggregates. It has a Mohs hardness of 5 to 6 and a specific gravity of 2.97 to 3.15. Refractive index values are nω = 1.378 and nε = 1.390.

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It was first described in 1868 and named for Italian mining engineer and mineralogist Quintino Sella (1827-1884). The type locality is Gébroulaz glacier, Val Thorens, Savoie, Rhône-Alpes, France.

References

• Palache, C., H. Berman, and C. Frondel (1951) Dana’s system of mineralogy, (7th edition), v. II, pp. 37–39
• Webmineral data
• Mindat with location data
• Mineral Data Publishing PDF