manganosite
noun
man·ga·no·site
ˌmaŋgəˈnōˌsīt,
manˈganəˌ-
plural -s
: a mineral MnO consisting of manganous oxide occurring in small emerald green octahedrons that turn black on exposure (hardness 5–6, specific gravity 5.18)
Word History
Etymology
German manganosit, from mangan- + connective -s- + -it -ite