Psilomelane, also known as black hematite and black malachite as well as commercially known as crown-of-silver,
is a group name for hard black manganese oxides such as hollandite and romanechite. Psilomelane consists of hydrous manganese oxide
with variable amounts of barium and potassium. The mineral is readily distinguished from other hydrous
manganese oxides by its greater hardness 5 to 6. Psilomelane is amorphous and occurs as botryoidal and stalactitic
masses with a smooth shining surface and submetallic lustre, giving it unique patterns creating a matchless
gemstone.
