Carlfrancisite
Carlfrancisite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mn²⁺₃(Mn²⁺,Mg,Fe³⁺,Al)₄₂(As³⁺O₃)₂(As⁵⁺O₄)₄[(Si,As⁵⁺)O₄]₆[(As⁵⁺,Si)O₄]₂(OH)₄₂.
It crystallizes in the hexagonal crystal system (space group R-3c). It is a member of the Hematolite structural group.
Key properties: Mohs hardness 3; specific gravity 3.62; Very pale yellow streak; Vitreous to opalescent luster; optically uniaxial.
IMA symbol Cfc, IMA status: approved, named in 2012.
Found in metamorphosed lenses in association with Cu-Pb-Ag sulfide ores in feldspathic sandstone that have been reworked by late hydrothermal solutions.
It is found associated with Alleghanyite, chlorite, pyrochroite, “spinels”, ribbeite.
The mineral was named to honor Colonel Eckhard D. Stuart (b. 1939) of Madison, Mississippi, USA., a mineral collector who has provided numerous samples for research, including this new species.