Manganite is a
mineral. Its composition is
manganese oxide-
hydroxide, MnO(OH), crystallizing in the
monoclinic system (pseudo-
orthorhombic). Crystals of manganite are prismatic and deeply striated parallel to their length; they are often grouped together in bundles. The color is dark steel-grey to iron-black, and the
luster brilliant and submetallic. The streak is dark reddish-brown. The
hardness is 4, and the
specific gravity is 4.3. There is a perfect cleavage parallel to the brachypinacoid, and less-perfect cleavage parallel to the prism faces.
Twinned crystals are not infrequent.