Pyrolusite is a
mineral consisting essentially of
manganese dioxide (
MnO2) and is important as an
ore of manganese. It is a black,
amorphous appearing mineral, often with a granular, fibrous or columnar structure, sometimes forming reniform crusts. It has a metallic
lustre, a black or bluish-black streak, and readily soils the fingers. The
specific gravity is about 4.8. Its name is from the Greek for
fire and to
wash, in reference to its use as a way to remove tints from glass.