A calcium- and manganese-containing mineral occurring as soft dark brown flakes and as compact or friable masses.
Ranciéite is a hydrated oxide of calcium and manganese, (Ca,Mnii)Mniv₄O₉·3H₂O. Crystal system: hexagonal.
Mid 19th century; earliest use found in Henry William Bristow (1817–1889), geologist. From French ranciéite, alteration of †rancierite from Rancié (formerly also †Rancier), name of the mountain near Vicdessos, Ariège, France, where the mineral was first found + -ite.