Francisite Locality: Iron Monarch open cut, Iron Knob , Middleback Range, Eyre peninsula , South Australia , Australia ( Locality at mindat.org ) Rare Francisite from the TL. Field of view 3 mm. Specimen and photo Leon Hupperichs. My thanks to Volker Hoppe for this exchange specimen. — Photo: Leon Hupperichs · CC BY-SA 3.0
Francisite
Francisite is an IMA-recognized mineral species in the halide class, with the chemical formula Cu₃Bi(Se⁴⁺O₃)₂O₂Cl.
It crystallizes in the orthorhombic crystal system (space group Pmmn).
Key properties: Mohs hardness 3–4; specific gravity 5.42; Pale apple-green streak; Adamantine luster.
IMA symbol Fcs, IMA status: approved, named in 1989.
Found as a rare secondary mineral in an oxidized barite lens in Precambrian sedimentary iron formation.
It is found associated with Chorargyrite, muscovite, naumannite, bismuth, djurleite, Cu–Bi–Ag selenides, barite.
The mineral was named to honor Glyn Francis (1939–), Quality Control Officer at the Iron Monarch quarry, Australia, who collected the first specimen.