Franciscanite
Franciscanite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mn²⁺₆(V⁵⁺ )(SiO₄)₂O₃(OH)₃.
It crystallizes in the hexagonal crystal system (space group P3). It is a member of the Welinite structural group.
Key properties: Mohs hardness 4; specific gravity 4.1; Brownish red streak; Vitreous luster; optically uniaxial.
IMA symbol Fcc, IMA status: approved, named in 1985.
Occurs as sparse, irregular segregations within a sheared sonolite-bearing assemblage in chert.
It is found associated with Sonolite, hausmannite, braunite, gageite.
The name refers to the Franciscan complex of California, USA, where it was found.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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