Mcgillite is a rare, monoclinic, pseudohexagonal mineral of the Pyrosmalite group, with the formula Mn2+
8Si
6O
15(OH)
8Cl
2. It was first approved in 1979, and is named for McGill University.
Mcgillite is found in the Sullivan Mine, Kimberley, Kootenay district, British Columbia, Canada; the Kyurazawa mine, Tochigi Prefecture, Japan; and at one location in Romania. At the Sullivan mine, it forms as fracture fillings in a manganese-rich portion of quartzite and argillite within a metamorphosed lead-zinc deposit. It is pink in color.
