Pyrolusite

Pyrolusite is a mineral consisting essentially of manganese dioxide (MnO2) and is important as an ore of manganese.[6] 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.[4]

Pyrolusite radiating
Acicular radiating pyrolusite
Pyrolusite
Pyrolusite - USGS ID Stose, GW 1425
General
CategoryOxide minerals
Formula
(repeating unit)
MnO2
Strunz classification4.DB.05
Crystal systemTetragonal
Crystal classDitetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)
Space groupP42/mnm
Identification
ColorDarkish, black to lighter grey, sometimes bluish
Crystal habitGranular to massive: botryoidal. Crystals rare
Twinning{031}, {032} may be polysynthetic
CleavagePerfect on 110
FractureBrittle
Mohs scale hardness6–6.5, 2 when massive
LusterMetallic, dull to earthy
StreakBlack to bluish-black
Specific gravity4.4–5.06
Refractive indexOpaque
References[1][2][3][4]
Major varieties
Polianitepseudomorphic after manganite[5]

Occurrence

Pyrolusite under normal light
A microscopic image of Pyrolusite

Pyrolusite and romanechite are among the most common manganese minerals. Pyrolusite occurs associated with manganite, hollandite, hausmannite, braunite, chalcophanite, goethite and hematite under oxidizing conditions in hydrothermal deposits. It also occurs in bogs and often results from alteration of manganite.[4]

Use

The metal is obtained by reduction of the oxide with sodium, magnesium, aluminium, or by electrolysis. Pyrolusite is extensively used for the manufacture of spiegeleisen and ferromanganese and of various alloys such as manganese-bronze. As an oxidizing agent it is used in the preparation of chlorine; 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 require synthetic products. Pyrolusite is also used to prepare disinfectants (permanganates) and for decolorizing glass. When mixed with molten glass it oxidizes the ferrous iron 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, and black colors to glass, pottery, and bricks; and in the manufacture of green and violet paints.

Dendritic manganese oxides

Black, manganese oxides with a dendritic crystal habit often found on fracture or rock surfaces are often assumed to be pyrolusite although careful analyses of numerous examples of these dendrites has shown that none of them are in fact pyrolusite. Instead, they are other forms of manganese oxide.[7][8]

History

Some of the most famous early cave paintings in Europe were executed by means of manganese dioxide. Blocks of pyrolusite are often found at Neanderthal sites. It may have been kept as a pigment for cave paintings, but it has also been suggested that it was powdered and mixed with tinder fungus for lighting fires.[9] Manganese dioxide, in the form of umber, was one of the earliest natural substances used by human ancestors. It was used as a pigment at least from the middle paleolithic. It may have been also used by the Neanderthals in fire-making.[10]

The ancient Greeks had a term μάγνης or Μάγνης λίθος ("Magnes lithos") meaning stone of the area called Μαγνησία (Magnesia), referring to Magnesia in Thessaly or to areas in Asia Minor with that name. Two minerals are called μάγνης, namely lodestone and pyrolusite (manganese dioxide). Later the term μαγνησία was used for manganese dioxide. In the 16th century it was called "manganesum". It was also called Alabandicus (from the Alabanda region of Asia Minor) and Braunstein. Eventually the name of the element manganese was derived from "manganesum", whereas "magnesia" came to mean the oxide of a different element, magnesium.[11]

See also

Other manganese oxides:

References

  1. ^ Mineralienatlas
  2. ^ http://webmineral.com/data/Pyrolusite.shtml Webmineral data
  3. ^ http://www.mindat.org/min-3318.html Mindat
  4. ^ a b c http://rruff.geo.arizona.edu/doclib/hom/pyrolusite.pdf Handbook of Mineralogy
  5. ^ http://www.mindat.org/min-6101.html Mindat polianite
  6. ^ Reidies, Arno H. (2002), "Manganese Compounds", Ullmann's Encyclopedia of Industrial Chemistry, 20, Weinheim: Wiley-VCH, pp. 495–542, doi:10.1002/14356007.a16_123, ISBN 3-527-30385-5.
  7. ^ Potter, Russell M. and Rossman, George R. (1979) Mineralogy of manganese dendrites and coatings. American Mineralogist, 64 (11-12). pp. 1219-1226
  8. ^ Mn dendrites on Mindat
  9. ^ Michael Le Page (Jul 28, 2018). "The original fire starters". New Scientist.
  10. ^ Selection and Use of Manganese Dioxide by Neanderthals
  11. ^ Calvert, J. B. (24 January 2003). "Chromium and Manganese". Archived from the original on 31 December 2016.

 This article incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). "Pyrolusite". Encyclopædia Britannica. 22 (11th ed.). Cambridge University Press. p. 693.

Akhtenskite

Akhtenskite is a manganese oxide mineral with the chemical formula of MnO2 (or: ε-Mn4+O2) that was named after the Akhtensk deposit in Russia, where it was first discovered and noted in 1979. It can be found in the Akhtensk brown ironstone deposit, in the southern Ural Mountains, on Mt. Zarod, on the Sikhote-Alin Mountains, and in the Primorskiy Krai, all in Russia.Its crystals are usually hexagonal in shape, with flakiness and plating, usually because it replaced a mineral. Akhtenskite is a polymorphous with the much more widespread pyrolusite. It occurs in mixtures with "psilomelane" (recently renamed to romanechite) and with other manganese oxides in an iron oxide deposit, most likely bacterially altered from a previous mineral in the Akhtensk deposit. It also occurs in crusts of ferromanganese minerals on oceanic rocks. Its chemical makeup is 63% oxygen and 37% manganese.

Some minerals that are commonly associated with akhtenskite are: todorokite, pyrolusite, nsutite, goethite, and cryptomelane.

Chemical chameleon

The chemical chameleon is a redox reaction, well known from classroom demonstrations, that exploits the dramatic color changes associated with the various oxidation states of manganese.Glauber reported the first description of the production of potassium permanganate when he noted that manganese dioxide (as the mineral pyrolusite) could be reacted at high temperatures with alkali to obtain a material that dissolved in water to give a green solution which slowly shifted to a violet-red. This process, similar to that still used in the production of potassium permanganate, oxidized manganese dioxide to potassium manganate which, acidified by carbon dioxide absorbed from the air, oxidized further to purple potassium permanganate.

The chemical chameleon reaction shows the process in reverse, by reducing violet potassium permanganate first to green potassium manganate and eventually to brown manganese dioxide:

KMnO4 (violet) → K2MnO4 (green) → MnO2 (brown/yellow suspension)Blue potassium hypomanganate may also form as an intermediate.

The reaction proceeds in alkaline conditions under the influence of a reducing agent. Sodium hydroxide, potassium hydroxide, and ammonium hydroxide can be used to alkalize the permanganate solution, while a variety of reducing agents can be used, sugars being common.A similar demonstration involves soaking paper in alkalized permanganate solution, which produces the same color changes as the paper is oxidized and the permanganate reduced.

Cryptomelane

Cryptomelane is a potassium manganese oxide mineral with formula K(Mn4+,Mn2+)8O16.

In 1942 the name cryptomelane was proposed as part of an effort to sort out the manganese oxide minerals referred to as psilomelane. Cryptomelane was identified and defined based on X-ray diffraction studies of samples from Tombstone, Arizona; Deming, New Mexico; Mena, Arkansas; and Philipsburg, Montana.Cryptomelane was approved in 1982 by the International Mineralogical Association (IMA). The type locality is the Tombstone District, Cochise County, Arizona, US. The name comes from the Greek for hidden and black, in reference to the confusion and difficulty in recognition of the various black manganese oxide minerals referred to as psilomelane, the collective term for hard manganese oxides.It is of rather common occurrence in oxidized manganese deposits where it occurs as replacements and open space fillings in veins and vugs. It occurs in association with pyrolusite, nsutite, braunite, chalcophanite, manganite and various other manganese oxides.

Felsite

Felsite is a very fine-grained volcanic rock that may or may not contain larger crystals. Felsite is a field term for a light-colored rock that typically requires petrographic examination or chemical analysis for more precise definition. Color is generally white through light gray, or red to tan and may include any color except dark gray, green or black (the colors of trap rock). The mass of the rock consists of a fine-grained matrix of felsic materials, particularly quartz, sodium and potassium feldspar, and may be termed a quartz felsite or quartz porphyry if the quartz phenocrysts are present. This rock is typically of extrusive origin, formed by compaction of fine volcanic ash, and may be found in association with obsidian and rhyolite. In some cases, it is sufficiently fine-grained for use in making stone tools. Its fine texture and felsic components allow for good knapped pieces, much like working chert, producing conchoidal fracture.

Dendritic manganese oxides such as pyrolusite and/or iron oxides such as limonite may precipitate along rock crevices, giving some rock chunk surfaces multicolored or arborescent patterned textures.

Gossan

Gossan (eiserner hut or eisenhut) is intensely oxidized, weathered or decomposed rock, usually the upper and exposed part of an ore deposit or mineral vein. In the classic gossan or iron cap all that remains is iron oxides and quartz, often in the form of boxworks (which are quartz-lined cavities retaining the shape of the dissolved ore minerals). In other cases quartz and iron oxides, limonite, goethite, and jarosite, exist as pseudomorphs replacing the pyrite and primary ore minerals. Frequently gossan appears as a red stain against the background rock and soil due to the abundance of oxidized iron and the gossan may be a topographic positive area due to the abundance of erosion resistant quartz and iron oxides. Although most gossans are red, orange, or yellow, black gossans from manganese oxides such as pyrolusite, manganite, and especially psilomelane form at the oxidized portion of manganese-rich mineral deposits.

In the 19th and 20th centuries gossans were important guides to buried ore deposits used by prospectors in their quest for metal ores. An experienced prospector could read the clues in the structure of the gossans to determine the type of mineralization likely to be found below the iron cap.

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. Hausmannite is a brown to black metallic mineral with Mohs hardness of 5.5 and a specific gravity of 4.8.

The type locality is Oehrenstock (Öhrenstock), Ilmenau, Thuringian Forest, Thuringia, Germany, where it was first described in 1813. Locations include Batesville, Arkansas, US; Ilfeld, Germany; Langban, Sweden; and the Ural Mountains, Russia. High quality samples have been found in South Africa and Namibia where it is associated with other manganese oxides, pyrolusite and psilomelane and the iron-manganese mineral bixbyite. Wilhelm Haidinger (1827) named it in honour of Johann Friedrich Ludwig Hausmann (1782–1859), Professor of Mineralogy, University of Göttingen, Germany.

Jacobsite

Jacobsite is a manganese iron oxide mineral. It is in the spinel group and forms a solid solution series with magnetite. The chemical formula is MnFe2O4 or with oxidation states and substitutions:

(Mn2+,Fe2+,Mg)(Fe3+,Mn3+)2O4.It occurs as a primary phase or as alteration of other manganese minerals during metamorphism of manganese deposits. Typical associated minerals include hausmannite, galaxite, braunite, pyrolusite, coronadite, hematite and magnetite.It was first described in 1869 and named for the Jakobsberg Mine, Nordmark, Filipstad, Värmland, Sweden.

Manganese

Manganese is a chemical element with symbol Mn and atomic number 25. It is not found as a free element in nature; it is often found in minerals in combination with iron. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.

Historically, manganese is named for pyrolusite and other black minerals from the region of Magnesia in Greece, which also gave its name to magnesium and the iron ore magnetite. By the mid-18th century, Swedish-German chemist Carl Wilhelm Scheele had used pyrolusite to produce chlorine. Scheele and others were aware that pyrolusite (now known to be manganese dioxide) contained a new element, but they were unable to isolate it. Johan Gottlieb Gahn was the first to isolate an impure sample of manganese metal in 1774, which he did by reducing the dioxide with carbon.

Manganese phosphating is used for rust and corrosion prevention on steel. Ionized manganese is used industrially as pigments of various colors, which depend on the oxidation state of the ions. The permanganates of alkali and alkaline earth metals are powerful oxidizers. Manganese dioxide is used as the cathode (electron acceptor) material in zinc-carbon and alkaline batteries.

In biology, manganese(II) ions function as cofactors for a large variety of enzymes with many functions. Manganese enzymes are particularly essential in detoxification of superoxide free radicals in organisms that must deal with elemental oxygen. Manganese also functions in the oxygen-evolving complex of photosynthetic plants. While the element is a required trace mineral for all known living organisms, it also acts as a neurotoxin in larger amounts. Especially through inhalation, it can cause manganism, a condition in mammals leading to neurological damage that is sometimes irreversible.

Manganese dioxide

Manganese(IV) oxide is the inorganic compound with the formula MnO2. This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for MnO2 is for dry-cell batteries, such as the alkaline battery and the zinc-carbon battery. MnO2 is also used as a pigment and as a precursor to other manganese compounds, such as KMnO4. It is used as a reagent in organic synthesis, for example, for the oxidation of allylic alcohols. MnO2 in the α polymorph can incorporate a variety of atoms (as well as water molecules) in the "tunnels" or "channels" between the manganese oxide octahedra. There is considerable interest in α-MnO2 as a possible cathode for lithium ion batteries.

Manganese oxide

Manganese oxide is any of a variety of manganese oxides and hydroxides. These include

Manganese(II) oxide, MnO (aka Ferrite Grade)

Manganese(II,III) oxide, Mn3O4

Manganese(III) oxide, Mn2O3

Manganese dioxide, (manganese(IV) oxide), MnO2

Manganese(VI) oxide, MnO3

Manganese(VII) oxide, Mn2O7It may refer more specifically to the following manganese minerals:

Birnessite

Hausmannite

Manganite

Manganosite

Psilomelane

PyrolusiteManganese may also form mixed oxides with other metals such as Fe, Nb, Ta, ... :

Bixbyite, a manganese iron oxide mineral

Jacobsite, a manganese iron oxide mineral

Columbite, also called niobite, niobite-tantalite and columbate

Tantalite, a mineral group close to columbite

Coltan, a mixture of columbite and tantalite

Galaxite, a spinel mineral

Todorokite, a rare complex hydrous manganese oxide mineral

Manganite

Manganite is a mineral composed of manganese oxide-hydroxide, MnO(OH), crystallizing in the monoclinic system (pseudo-orthorhombic). 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 luster brilliant and submetallic. The streak is dark reddish brown. The hardness is 4, and the specific gravity is 4.3. There is a perfect cleavage parallel to the brachypinacoid, and less-perfect cleavage parallel to the prism faces. Twinned crystals are not infrequent.

The mineral contains 89.7% manganese sesquioxide; it dissolves in hydrochloric acid with evolution of chlorine.

Non-ferrous metal

In metallurgy, a non-ferrous metal is a metal, including alloys, that does not contain iron (ferrite) in appreciable amounts.

Generally more costly than ferrous metals are used because of desirable properties such as low weight (e.g. aluminium), higher conductivity (e.g. copper), non-magnetic property or resistance to corrosion (e.g. zinc). Some non-ferrous materials are also used in the iron and steel industries. For example, bauxite is used as flux for blast furnaces, while others such as wolframite, pyrolusite and chromite are used in making ferrous alloys.Important non-ferrous metals include aluminium, copper, lead, nickel, tin, titanium and zinc, and alloys such as brass. Precious metals such as gold, silver and platinum and exotic or rare metals such as cobalt, mercury, tungsten, beryllium, bismuth, cerium, cadmium, niobium, indium, gallium, germanium, lithium, selenium, tantalum, tellurium, vanadium, and zirconium are also non-ferrous. They are usually obtained through minerals such as sulfides, carbonates, and silicates. Non-ferrous metals are usually refined through electrolysis.

Oxide minerals

The oxide mineral class includes those minerals in which the oxide anion (O2−) is bonded to one or more metal ions. The hydroxide-bearing minerals are typically included in the oxide class. The minerals with complex anion groups such as the silicates, sulfates, carbonates and phosphates are classed separately.

Simple oxides:

X2O and XO

Cuprite Cu2O

Ice H2O

Periclase group

Periclase MgO

Manganosite MnO

Zincite group

Zincite ZnO

Bromellite BeO

Tenorite CuO

Litharge PbO

X2O3Hematite group

Corundum Al2O3

Hematite Fe2O3

Ilmenite FeTiO3

XO2Rutile group

Rutile TiO2

Pyrolusite MnO2

Cassiterite SnO2

Baddeleyite ZrO2

Uraninite UO2

Thorianite ThO2

XY2O4Spinel group

Spinel MgAl2O4

Gahnite ZnAl2O4

Magnetite Fe3O4 (Fe2+Fe3+2O4)

Franklinite (Zn,Fe,Mn)(Fe,Mn)2O4

Chromite FeCr2O4

Chrysoberyl BeAl2O4

Columbite(Fe,Mn)(Nb,Ta)2O6Hydroxide subgroup:

Brucite Mg(OH)2

Manganite MnO(OH)

Romanechite BaMn2+Mn4+8O16(OH)4

Goethite group

Diaspore αAlO(OH)

Goethite αFeO(OH)

Potassium permanganate

Potassium permanganate is an inorganic chemical compound and medication. As a medication it is used for cleaning wounds and dermatitis.It has the chemical formula KMnO4 and is a salt consisting of K+ and MnO−4 ions. It is a strong oxidizing agent. It dissolves in water to give intensely pink or purple solutions, the evaporation of which leaves prismatic purplish-black glistening crystals. In 2000, worldwide production was estimated at 30,000 tonnes. In this compound, manganese is in the +7 oxidation state.

The wholesale cost in the developing world is about US$0.01 per gram of powder. In the United Kingdom a 400 milligram tablet costs the NHS roughly £0.51.

Psilomelane

Psilomelane is a group name for hard black manganese oxides including hollandite and romanechite. Psilomelane consists of hydrous manganese oxide with variable amounts of barium and potassium. Psilomelane is erroneously, and uncommonly, known as black hematite, despite not being related to true hematite, which is an iron oxide.

Romanèchite

Romanèchite ((Ba,H2O)2(Mn+4,Mn+3)5O10) 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 of 6 and a specific gravity of 4.7-5. It is associated with hematite, barite, pyrolusite, quartz and other manganese oxide minerals. It has been found in France, Germany, England, Brazil and various parts of the United States, including Arizona, Virginia, Tennessee and Michigan.

Rudolf Koechlin

Rudolf Koechlin (11 November 1862 – 11 February 1939) was an Austrian mineralogist.

Koechlin was born and died in Vienna. He studied mineralogy, crystallography, petrology and geology at the University of Vienna, obtaining his doctorate in 1887 with a thesis on manganite, polianite and pyrolusite. At Vienna, his instructors included Gustav Tschermak and Albrecht Schrauf. In 1884 he began work as a volunteer in the mineralogical-petrography department of the Naturhistorisches Hofmuseum in Vienna. In 1897 he became a "custos-adjunct", later named a curator first-class (1912), and in 1920, was appointed director of the mineralogical-petrography department.His scientific research largely dealt with minerals found in the Tauern region in Austria, e.g. bornite, euclase and sphene as well as the salt minerals glauberite and simonyite from the salt mine at Hallstatt. The mineral koechlinite is named in his honor.He was the author of around 70 scientific papers and made important contributions towards publication of the "Mineralogisches Taschenbuch" (first edition, 1911). From 1910 to 1932, he was a staff member of the Wiener Mineralogische Gesellschaft. In 1922, he became a correspondent member of the Austrian Academy of Sciences.

Todorokite

Todorokite is a rare complex hydrous manganese oxide mineral with the formula (Na,Ca,K,Ba,Sr)1-x(Mn,Mg,Al)6O12·3-4H2O. It was named in 1934 for the type locality, the Todoroki mine, Hokkaido, Japan. It belongs to the prismatic class 2/m of the monoclinic crystal system, but the angle β between the a and c axes is close to 90°, making it seem orthorhombic. It is a brown to black mineral which occurs in massive or tuberose forms. It is quite soft with a Mohs hardness of 1.5, and a specific gravity of 3.49 - 3.82. It is a component of deep ocean basin manganese nodules.

Wad

Wad is an old mining term for any black manganese oxide or hydroxide mineral-rich rock in the oxidized zone of various ore deposits. Typically closely associated with various iron oxides. Specific mineral varieties include pyrolusite, lithiophorite, nsutite, takanelite and vernadite. Wad can be considered to be the manganese equivalent to the iron mineraloid limonite.

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