Pyrolusite is a mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

 consisting essentially of manganese dioxide (Mn

Manganese

Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

O

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

₂) and is important as an ore

Ore

An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....

 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

Lustre (mineralogy)

Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance....

, a black or bluish-black streak, and readily soils the fingers. The specific gravity

Specific gravity

Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...

 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.

Occurrence

Pyrolusite and romanechite

Romanèchite

Romanèchite is the primary constituent of psilomelane, which is a mixture of minerals. Most psilomelane is not pure romanechite, so it is incorrect to consider them synonyms. Romanèchite is a valuable ore of manganese, which is used in steelmaking. It has a monoclinic crystal structure, a hardness...

 are among the most common manganese minerals.
Pyrolusite occurs associated with manganite

Manganite

Manganite is a mineral. Its composition is manganese oxide-hydroxide, MnO, crystallizing in the monoclinic system . 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...

, hollandite, hausmannite

Hausmannite

Hausmannite is a complex oxide of manganese containing both di- and tri-valent manganese. The formula can be represented as Mn2+Mn3+2O4. It belongs to the spinel group and forms tetragonal crystals...

, braunite

Braunite

Braunite is a silicate mineral containing both di- and tri-valent manganese with the chemical formula:Mn2+Mn3+6[O8|SiO4]. Common impurities include iron, calcium, boron, barium, titanium, aluminium, and magnesium....

, chalcophanite, goethite

Goethite

Goethite , named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment samples...

 and hematite

Hematite

Hematite, also spelled as haematite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...

 under oxidizing

Redox

Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 conditions in hydrothermal deposits. It also occurs in bog

Bog

A bog, quagmire or mire is a wetland that accumulates acidic peat, a deposit of dead plant material—often mosses or, in Arctic climates, lichens....

s and often results from alteration of manganite.

Use

The metal is obtained by reduction of the oxide with sodium

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

, magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

, aluminium

Aluminium

Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

, or by electrolysis

Electrolysis

In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...

. Pyrolusite is extensively used for the manufacture of spiegeleisen

Spiegeleisen

Spiegeleisen is a ferromanganese alloy containing approximately 15% manganese and small quantities of carbon and silicon. Historically, this was the standard form in which manganese was traded and used in steel making...

 and ferromanganese

Ferromanganese

Ferromanganese, a ferroalloy with high content of manganese, is made by heating a mixture of the oxides MnO2 and Fe2O3, with carbon, usually as coal and coke, in either a blast furnace or an electric arc furnace-type system, called a submerged arc furnace. The oxides undergo carbothermal reduction...

 and of various alloys such as manganese-bronze

Bronze

Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...

. As an oxidizing agent it is used in the preparation of chlorine

Chlorine

Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

; indeed, chlorine gas itself was first described by Karl Scheele in 1774 from the reaction products of pyrolusite and hydrochloric acid. Natural pyrolusite has been used in batteries, but high-quality batteries requires synthetic products. Pyrolusite is also used to prepare disinfectants (permanganate

Permanganate

A permanganate is the general name for a chemical compound containing the manganate ion, . Because manganese is in the +7 oxidation state, the permanganate ion is a strong oxidizing agent. The ion has tetrahedral geometry...

s) and for decolorizing glass. When mixed with molten glass it oxidizes the ferrous iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 to ferric iron, and so discharges the green and brown tints (making it classically useful to glassmakers as a decolorizer). As a coloring material, it is used in calico printing and dyeing; for imparting violet, amber

Amber (color)

Amber is an orange-yellow color that got its name from the material known as amber. Due to this, amber can refer not to one but to a series of shades of orange, since the natural material varies from nearly yellow when newer to orange or reddish-orange when older.-Amber:Amber is a pure chroma color...

, and black colors to glass, pottery, and bricks; and in the manufacture of green and violet paints.