Outstanding sharp gemmy crystals of the rare mineral tunisite from one of the only three known localities worldwide: Condorcet, Auvergne-Rhône-Alpes, France. — Photo: David Hospital · CC BY-SA 4.0
Tunisite
Tunisite is an IMA-recognized mineral species in the carbonate class, with the chemical formula NaCa₂Al₄(CO₃)₄(OH)₈Cl.
It crystallizes in the tetragonal crystal system (space group P4/nmm).
Key properties: Mohs hardness 4.5; specific gravity 2.51; optically uniaxial.
IMA symbol Tun, IMA status: approved, named in 1967.
A very rare hydrothermal mineral, filling cavities in calcite (Sakiet Sidi Yousseff mine, Tunisia).
It is found associated with Calcite (Sakiet Sidi Yousseff mine, Tunisia); celestine, calcite, pyrite, chalcopyrite, gypsum, whewellite (Condorcet, France).
The name refers to Tunisia, the country in which it was first found to occur.