Sellaite is a magnesium fluoride mineral with the 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.
Hardness:
5 - 5.5
Density:
3.08 g/cm³
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Properties
Characteristics
Common Questions
General Info About Sellaite
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Physical Properties of Sellaite
Colors
Colourless, white, colourless in transmitted light
Streak
White
Hardness
5 - 5.5 , Soft
Density
3.08 g/cm³, Normal Weight
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Chemical Properties of Sellaite
Formula
MgF2
Elements listed
F, Mg
Optical Properties of Sellaite
Refractive Index
1.378-1.390
Birefringence
0.010-0.012
Optical Character
Uniaxial negative
Characteristics of Sellaite
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Formation of Sellaite
Sellaite was first described in 1868 and named for Italian mining engineer and mineralogist Quintino Sella (1827–1884). Its type locality is the glacier de Gébroulaz [fr] in France, where it occurred inside bitumen-bearing dolomite-anhydrite clasts within a moraine deposit. It has been reported in an evaporite deposit at Bleicherode; within volcanic ejecta and fumaroles at Vesuvius; in a metamorphic magnesite deposit at Serra das Éguas [pt]; and in sodic alkali granite near Gjerdingen [no].
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