Exhibit in the Redpath Museum, McGill University - Montreal, Quebec, Canada. — Photo: Daderot · CC0
Mcgillite
A rare manganese pyrosmalite-group silicate named for McGill University.
Intro adapted from Wikipedia (CC BY-SA).
Mcgillite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mn²⁺₈Si₆O₁₅(OH)₈Cl₂.
It crystallizes in the monoclinic crystal system. It is a member of the Pyrosmalite, Clay structural group.
Key properties: Mohs hardness 4; specific gravity 2.98; Pearly on cleavage surfaces luster; optically biaxial.
IMA symbol Mcg, IMA status: approved, named in 1979.
Occurs as open-space fracture fillings in a manganese-rich section of quartzite and argillite in a metamorphosed Pb{Zn orebody (Sullivan mine, Canada).
It is found associated with Sphalerite, boulangerite, galena, jamesonite, quartz (Sullivan mine, Canada).
The name refers to McGill University, Montreal, Quebec, Canada.