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Fontanite
Fontanite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Ca(UO₂)₃(CO₃)₂O₂·6H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/n).
Key properties: Mohs hardness 3; specific gravity 4.1; White streak; Vitreous luster; optically biaxial.
IMA symbol Ftn, IMA status: approved, named in 1991.
A rare secondary mineral found in the oxidized portions of a uranium deposit.
It is found associated with Billietite, uranophane.
The mineral was named to honor François Fontan (1942-2007), mineralogist specializing in phosphates, University Paul-Sabatier, Toulouse, France.