pyrolusite

{{Infobox mineral | name = Pyrolusite | category = Oxide minerals | boxwidth = | boxbgcolor = | image = Pyrolusite - USGS ID Stose, GW 1425.jpg | imagesize = | caption = | formula = MnO2 | IMAsymbol = Pyl | molweight = | strunz = 4.DB.05 | system = Tetragonal | class = Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) | symmetry = P42/mnm | color = Darkish, black to lighter grey, sometimes bluish | habit = Granular to massive: botryoidal. Crystals rare | twinning = {031}, {032} may be polysynthetic | cleavage = Perfect on {110} | fracture = Irregular/Uneven | tenacity = Brittle | mohs = 6–6.5, 2 when massive | luster = Metallic, dull to earthy | refractive = Opaque | opticalprop = | birefringence = | pleochroism = | streak = Black to bluish-black | gravity = 4.4–5.06 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = | other = | references = | var1 = Polianite | var1text = pseudomorphic after manganite }}

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 luster, 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. thumb|Acicular radiating pyrolusite