Images
Formula: MgF2
Fluoride
Crystal System: Tetragonal
Specific gravity: 3.15 measured, 3.08 calculated
Hardness: 5
Streak: White
Colour: Colourless or white, colourless in transmitted light
Solubility: Slightly soluble in water. Decomposed by concentrated sulphuric acid
Environments
Igneous environments
Pegmatites
Evaporite deposits
Fumeroles
Sellaite occurs in evaporites, volcanic ejecta and fumeroles, marble,
magnesite and alkalic granite.
Anhydrite, gypsum and
sulphur are common associates
(Mindat).
Localities
At the Pedra Preta pit, Serra das Éguas, Brumado, Bahia, Brazil, sellaite occurs
in vugs associated with magnesite and
quartz
(Dana).
At the type locality, the Gébroulaz glacier, Val Thorens, Saint-Martin-de-Belleville, Les Belleville, Albertville, Savoie, Auvergne-Rhône-Alpes, France,
sellaite occurs in bituminous
dolomite-anhydrite
rock in a glacial moraine (Dana). Associated minerals include fluorite,
anhydrite, dolomite,
celestine, quartz and
sulphur
(Mindat).
At Carrara, Massa-Carrara Province, Tuscany, Italy, sellaite occurs in cavities in marble
(Dana).
Back to Minerals