Goethite (, ) is a mineral of the

diaspore Diaspore , also known as diasporite, empholite, kayserite, or tanatarite, is an aluminium oxide hydroxide mineral, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. It occurs sometimes as flattened crystals, but ...

group, consisting of

iron(III) oxide-hydroxide Iron(III) oxide-hydroxide or ferric oxyhydroxideA. L. Mackay (1960): "β-Ferric Oxyhydroxide". ''Mineralogical Magazine'' (''Journal of the Mineralogical Society''), volume 32, issue 250, pages 545-557. is the chemical compound of iron, oxygen ...

, specifically the "α" polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient times for its use as a

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...

(brown

ochre Ochre ( ; , ), or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colours produced ...

). Evidence has been found of its use in paint pigment samples taken from the caves of Lascaux in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

. It was first described in 1806 based on samples found in the Hollertszug Mine in

Herdorf Herdorf () is a town in the district of Altenkirchen, in Rhineland-Palatinate, Germany. It is situated on the river Heller, approx. 20 km south-west of Siegen. Twin towns — sister cities Herdorf is twinned with: * Saint-Laurent-du- ...

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwee ...

. The mineral was named after the

German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...

polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a substantial number of subjects, known to draw on complex bodies of knowledge to solve specific pro ...

and poet

Johann Wolfgang von Goethe Johann Wolfgang von Goethe (28 August 1749 – 22 March 1832) was a German poet, playwright, novelist, scientist, statesman, theatre director, and critic. His works include plays, poetry, literature, and aesthetic criticism, as well as t ...

(1749–1832).

Composition

Goethite is an iron oxyhydroxide containing ferric iron. It is the main component of

rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO( ...

and

bog iron Bog iron is a form of impure iron deposit that develops in bogs or swamps by the chemical or biochemical oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. O ...

ore. Goethite's hardness ranges from 5.0 to 5.5 on the

Mohs Scale The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by ...

, and its

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its dens ...

varies from 3.3 to 4.3. The mineral forms prismatic needle-like

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

s ("needle ironstone") but is more typically massive.

Feroxyhyte Feroxyhyte is an oxide/hydroxide of iron, δ-Fe3+O(OH). Feroxyhyte crystallizes in the hexagonal system. It forms as brown rounded to concretionary masses. Feroxyhyte is opaque, magnetic, has a yellow streak, and has a relative density of 4.2. ...

and

lepidocrocite Lepidocrocite (γ-FeO(OH)), also called esmeraldite or hydrohematite, is an iron oxide-hydroxide mineral. Lepidocrocite has an orthorhombic crystal structure, a hardness of 5, specific gravity of 4, a submetallic luster and a yellow-brown ...

are both polymorphs of the iron oxyhydroxide FeO(OH) which are stable at the pressure and temperature conditions of the Earth's surface. Although they have the same chemical formula as goethite, their different crystalline structures make them distinct minerals. Additionally, goethite has several high-pressure and high-temperature polymorphs, which may be relevant to the conditions of the Earth's interior. These include ε-FeOOH, which has an orthorhombic crystal structure, a cubic

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...

-type polymorph with or without losing hydrogen and an ultradense hexagonal structure. Goethite has the same crystal structure as

, the analogous aluminium oxide-hydroxide mineral. Oxygen and hydroxide ions form a hexagonal close-packed structure, with iron ions filling octahedral sites between the anions. The sites filled by iron ions form paired chains running the length of the crystal, with the two chains in each pair joined by hydroxide ions. File:Goethite c.png, The goethite crystal structure viewed along 01 Red ions are iron, white are oxygen, and yellow are hydroxide. File:Goethite b.png, The goethite crystal structure viewed along 10

Formation

Goethite often forms through the

weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs '' in situ'' (on site, with little or no movement ...

of other iron-rich minerals, and thus is a common component of

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...

s, concentrated in

laterite Laterite is both a soil and a rock type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by ...

soils. nanoparticulate

authigenic Authigenesis is the process whereby a mineral or sedimentary rock deposit is generated where it is found or observed. Such deposits are described as authigenic. Authigenic sedimentary minerals form during sedimentation by precipitation or rec ...

goethite is a common diagenetic iron oxyhydroxide in both marine and lake sediments. The formation of goethite is marked by the oxidation state change of Fe²⁺ (ferrous) to Fe³⁺ (ferric), which allows for goethite to exist at surface conditions. Because of this oxidation state change, goethite is commonly seen as a

pseudomorph In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form ( crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced ...

. As iron-bearing minerals are brought to the zone of oxidation within the soil, the iron turns from iron(II) to iron(III), while the original shape of the parent mineral is retained. Examples of common goethite pseudomorphs are: goethites after pyrite, goethite, siderite, and marcasite, though any iron(II)-bearing mineral could become a goethite pseudomorph if proper conditions are met. It may also be precipitated by

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit ...

or in other sedimentary conditions, or form as a primary mineral in

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

deposits. Goethite has also been found to be produced by the excretion processes of certain bacteria types.

Distribution

Goethite is found all over the planet, usually in the form of

concretion A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular ...

s, stalactitic formations,

oolite Oolite or oölite (''egg stone'') is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Ancient Greek word for egg (ᾠόν). Strictly, oolites consist of ooids of diameter 0.25� ...

s (a form consisting of tiny round grains cemented together), reniform (kidney shapes) or botryoidal (globular, like bunches of grapes) accumulations. It is also a very common pseudomorph. It is frequently encountered in the swampy areas at the head of spring waters ('

'), on cave floors, and on the bottom of lakes and small creeks. The ''boxworks'' or gossan resulting from the

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...

of sulfide ore deposits is formed of goethite along with other iron oxides and quartz. Significant deposits of goethite are found in

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

;

Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribb ...

; and

Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over t ...

Missouri Missouri is a state in the Midwestern region of the United States. Ranking 21st in land area, it is bordered by eight states (tied for the most with Tennessee): Iowa to the north, Illinois, Kentucky and Tennessee to the east, Arkansas t ...

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...

Alabama (We dare defend our rights) , anthem = " Alabama" , image_map = Alabama in United States.svg , seat = Montgomery , LargestCity = Huntsville , LargestCounty = Baldwin County , LargestMetro = Greater Birmingham , area_total_km2 = 135,7 ...

Georgia Georgia most commonly refers to: * Georgia (country), a country in the Caucasus region of Eurasia * Georgia (U.S. state), a state in the Southeast United States Georgia may also refer to: Places Historical states and entities * Related to the ...

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth are ...

, and

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. Tennessee is the List of U.S. states and territories by area, 36th-largest by ...

, in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

. Deposits significant in location, if not in abundance, have been found in the

Martian Mars, the fourth planet from the Sun, has appeared as a setting in works of fiction since at least the mid-1600s. It became the most popular celestial object in fiction in the late 1800s as the Moon was evidently lifeless. At the time, the pr ...

crater Gusev by NASA's '' Spirit'' rover, providing strong evidence for the presence of liquid water on the planet in an earlier stage of its evolution. Limpets' teeth are composed of about 80% goethite fibres of only tens of nanometers in diameter, small enough to be flaw-insensitive, which accounts for their extreme

tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials ...

of 3.5–6.0 GPa and

elastic modulus An elastic modulus (also known as modulus of elasticity) is the unit of measurement of an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is ...

of 120±30 GPa.

Usage

Its main modern use is as an

iron ore Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the ...

, being referred to as ''brown iron ore''. Goethite is an important component of

pigments, and has been heat-treated for use as a red pigment since

Paleolithic The Paleolithic or Palaeolithic (), also called the Old Stone Age (from Greek: παλαιός '' palaios'', "old" and λίθος ''lithos'', "stone"), is a period in human prehistory that is distinguished by the original development of stone too ...

times. Iron-rich lateritic soils that have developed over

serpentinite Serpentinite is a rock composed predominantly of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake. Serpentinite has been called ''serpentine'' or ''s ...

rocks in tropical climates are mined for their iron content, as well as other metals. Fine goethite specimens are rare and therefore are valued collectibles. Banded or iridescent varieties are cut and polished into cabochons for jewelry making. In a royal tomb of the ancient kingdom of

Phrygia In classical antiquity, Phrygia ( ; grc, Φρυγία, ''Phrygía'' ) was a kingdom in the west central part of Anatolia, in what is now Asian Turkey, centered on the Sangarios River. After its conquest, it became a region of the great empir ...

, a body was found believed to be King

Gordias Gordias ( grc, Γορδίας, ''Gordías''; also Γόρδιος, ''Górdios'', "Gordius") was the name of at least two members of the royal house of Phrygia. The best-known Gordias was reputedly the founder of the Phrygian capital city Gordium, ...

, father of the legendary King Midas. The burial shroud had been colored with a dye containing goethite, which in its original unfaded state would have made the shroud look like it was woven from gold. Historians speculate that the legend of King Midas' golden touch might have originated from Phrygian royalty wearing clothes made from such golden-colored textiles.Archived a
Ghostarchive
and th
Wayback Machine

Gallery

File:Goethite-242608.jpg,

Iridescent Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...

goethite, Filón Sur Mine,

Tharsis, Huelva Tharsis is a village that is part of the Alosno municipality in the province of Huelva, Spain. According to the 2013 census, the village has a population of 1,840 inhabitants. Mining Tharsis is a mining town where the Filón Sur Mine, known for ...

, Spain File:Goethite3.jpg, Goethite from

Minas Gerais Minas Gerais () is a state in Southeastern Brazil. It ranks as the second most populous, the third by gross domestic product (GDP), and the fourth largest by area in the country. The state's capital and largest city, Belo Horizonte (literall ...

, Brazil File:Goethite-Calcite-Feldspar-Group-215498.jpg, A sharp, disc-shaped calcite has here been completely replaced by goethite, which preserved the original form perfectly File:PyOx.JPG, Goethite coating/replacing rusted

cubes File:Goethite-162473.jpg, Finely crystallized specimen of goethite from Lake George, Park County,

, USA File:Harvard Museum of Natural History. Goethite. Negaunee, Marquette Co., MI (DerHexer) 2012-07-20.jpg, Goethite from Negaunee, Marquette County, Michigan

References

External links

* {{Authority control Iron(III) minerals Iron oxide pigments Hydroxide minerals Johann Wolfgang von Goethe Orthorhombic minerals Minerals in space group 62 Iron ores Magnetic minerals Minerals described in 1806