cummingtonite
/ˈkʌmɪŋtənʌɪt
/noun [mass noun]
A mineral occurring typically as brownish fibrous crystals in some metamorphic rocks. It is a magnesium-rich iron silicate of the amphibole group.Accessory chlorite, magnetite or ilmenite, titanite, apatite, partly chloritized biotite, epidote, pyrite and sometimes cummingtonite, are present....
- This rock is a dark gray schistose rock containing radiating aggregates of cummingtonite and occasionally pyrrhotite.
- The two minerals can have similar distinctive brown colors and are hard to differentiate from each other, although cummingtonite is typically darker and slightly denser.
Origin
Early 19th century: named after Cummington, a town in Massachusetts, US, + -ite1.