Psilomelane

Psilomelane is a hydrous oxide of manganese containing varying amounts of barium, potassium and sodium oxides. It is steel grey to black in colour and its streak is black. Its hardness ranges from 5 to 7. Its specific gravity varies from 3.3 to 4.7 and its lustre is sub-metallic or dull.
Psilomelane is used as an ore of manganese. In India, it occurs in Andhra Pradesh and Madhya Pradesh