Jarosite is a basic hydrous

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...

and ferric

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

(Fe-III) with a chemical formula of KFe₃(SO₄)₂(OH)₆. This

sulfate mineral The sulfate minerals are a class of minerals that include the sulfate ion () within their structure. The sulfate minerals occur commonly in primary evaporite depositional environments, as gangue minerals in hydrothermal Vein (geology), veins and as ...

is formed in

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...

deposits by the

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

of iron

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

s. Jarosite is often produced as a byproduct during the purification and refining of

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

and is also commonly associated with

acid mine drainage Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines and coal mines. Acid rock drainage occurs naturally within some environments as part of the rock weatherin ...

and acid sulfate soil environments.

Physical properties

Jarosite has a

trigonal In crystallography, the hexagonal crystal family is one of the six crystal family, crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the tr ...

crystal structure and is brittle, with basal cleavage, a

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by Pressing (metalworking), pressing or abrasion ...

of 2.5–3.5, and a

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of 3.15–3.26. It is translucent to opaque with a vitreous to dull luster, and is colored dark yellow to yellowish-brown. It can sometimes be confused with

limonite Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as , although this is not entirely accurate as the ratio of oxide to hydroxide can vary qu ...

goethite Goethite (, ) is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the α- polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient t ...

with which it commonly occurs in the

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 ...

(oxidized cap over an ore body). Jarosite is an iron analogue of the potassium aluminium sulfate,

alunite Alunite is a hydroxylated aluminium potassium sulfate mineral, formula potassium, Kaluminium, Al3(sulfur, Soxygen, O4)2(Ohydrogen, H)6. It was first observed in the 15th century at Tolfa, near Rome, where it was mined for the manufacture of alum ...

Solid solution series

The alunite supergroup includes the

, jarosite, beudantite, crandallite and florencite subgroups. The alunite supergroup minerals are isostructural with each other and substitution between them occurs, resulting in several

solid solution A solid solution, a term popularly used for metals, is a homogeneous mixture of two compounds in solid state and having a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word "solutio ...

series. The alunite supergroup has the general formula AB₃(TO₄)₂(OH)₆. In the alunite subgroup B is Al, and in the jarosite subgroup B is Fe³⁺. The beudantite subgroup has the general formula AB₃(XO₄)(SO₄)(OH)₆, the crandallite subgroup AB₃(TO₄)₂(OH)₅•H₂O and the florencite subgroup AB₃(TO₄)₂(OH)_5 or 6. Jarosite crystal structure

In the jarosite-alunite series Al may substitute for Fe and a complete solid solution series between jarosite and alunite, KAl₃(SO₄)₂(OH)₆, probably exists, but intermediate members are rare. The material from Kopec,

Czech Republic The Czech Republic, also known as Czechia, and historically known as Bohemia, is a landlocked country in Central Europe. The country is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the south ...

, has about equal Fe and Al, but the amount of Al in jarosite is usually small. When jarosite forms from

pyrite The mineral pyrite ( ), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue ...

in sedimentary clays, the main sources of K⁺ are

illite Illite, also called hydromica or hydromuscovite, is a group of closely related non-expanding clay minerals. Illite is a secondary mineral precipitate, and an example of a phyllosilicate, or layered alumino-silicate. Its structure is a 2:1 sandw ...

, a non-swelling clay, or K-feldspar. In other geological settings

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...

's alteration can also be a source of potassium. In the jarosite-natrojarosite series Na substitutes for K to at least Na/K = 1:2.4 but the pure sodium end member NaFe₃(SO₄)₂(OH)₆ is not known in nature. Minerals with Na > K are known as natrojarosite. End member formation (jarosite and natrojarosite) is favoured by a low temperature environment, less than 100 °C, and is illustrated by the oscillatory zoning of jarosite and natrojarosite found in samples from the Apex Mine, Arizona, and Gold Hill, Utah. This indicates that there is a wide miscibility gap between the two end members,American Mineralogist (2007) 92:444–447 and it is doubtful whether a complete series exists between jarosite and natrojarosite. In hydroniumjarositeAmerican Mineralogist (2007) 92:1464–1473 the

hydronium In chemistry, hydronium (hydroxonium in traditional British English) is the cation , also written as , the type of oxonium ion produced by protonation of water. It is often viewed as the positive ion present when an Arrhenius acid is dissolved ...

ion H₃O⁺ can also substitute for K⁺, with increased hydronium ion content causing a marked decrease in the lattice parameter ''c'', although there is little change in ''a''.American Mineralogist (1965) 50:1595–1607 Hydroniumjarosite will only form from alkali-deficient solutions, as alkali-rich jarosite forms preferentially. Divalent cations may also substitute for the monovalent cation K⁺ in the A site.American Mineralogist (1987) 72:178–187 Charge balance may be achieved in three ways. :Firstly by replacing two monovalent cations by one divalent cation, and leaving an A site vacancy, as in plumbogummite, Pb²⁺Al₃(PO₄)₂(OH)₅.H₂O, which is a member of the crandallite subgroup. :Secondly by incorporating divalent ions in the B sites, as in osarizawaite, Pb²⁺Cu²⁺Al₂(SO₄)₂(OH)₆, alunite subgroup, and beaverite, Pb²⁺Cu²⁺(Fe³⁺,Al)₂(SO₄)₂(OH)₆, jarosite subgroup. :Thirdly by replacing divalent anions with trivalent anions, as in beudantite, PbFe³⁺₃(AsO₄)³⁻(SO₄)(OH)₆, beudantite subgroup.

History

Jarosite was first described in 1852 by August Breithaupt in the Barranco del Jaroso in the Sierra Almagrera (near Los Lobos, Cuevas del Almanzora,

Almería Almería (, , ) is a city and municipalities in Spain, municipality of Spain, located in Andalusia. It is the capital of the province of Almería, province of the same name. It lies in southeastern Iberian Peninsula, Iberia on the Mediterranean S ...

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

). The name jarosite is directly derived from "jara", the Spanish name of a yellow flower that belongs to the genus ''

Cistus ''Cistus'' (from the Greek ''kistos'') is a genus of flowering plants in the rockrose family Cistaceae, containing about 20 species (Ellul ''et al.'' 2002). They are perennial shrubs found on dry or rocky soils throughout the Mediterranean reg ...

'' and grows in the sierra. The mineral and the flower have the same color. Mysterious spheres of clay, in diameter and covered with jarosite, have been found beneath the Temple of the Feathered Serpent, an ancient six-level stepped pyramid from Mexico City.

Mars exploration

Ferric sulfate and jarosite have been detected by three martian rovers: '' Spirit'', '' Opportunity'' and ''

Curiosity Curiosity (from Latin , from "careful, diligent, curious", akin to "care") is a quality related to inquisitive thinking, such as exploration, investigation, and learning, evident in humans and other animals. Curiosity helps Developmental psyc ...

''. These substances are indicative of strongly oxidizing conditions prevailing at the surface of

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

. In May 2009, the ''Spirit'' rover became stuck when it drove over a patch of soft ferric sulfate that had been hidden under a veneer of normal-looking soil. Because iron sulfate has very little cohesion, the rover's wheels could not gain sufficient traction to pull the body of the rover out of the iron sulfate patch. Multiple techniques were attempted to extricate the rover, but the wheels eventually sank so deeply into the iron sulfate that the body of the rover came to rest on the Martian surface, preventing the wheels from exerting any force on the material below them. As the JPL team failed to recover the mobility of ''Spirit'', it signified the end of the journey for the rover.

Antarctica deep borehole

On Earth, jarosite is mainly associated with the ultimate stage of pyrite oxidation in clay environment, and can also be found in

mine tailings In mining, tailings or tails are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different from overburden, which is the waste rock or other material th ...

waste where acidic conditions prevail. Against all expectations, jarosite has also been fortuitously discovered in minute quantities in the form of small dust particles in ice cores recovered from a deep borehole in

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

. That surprising discovery was made by geologists who were searching for specific minerals capable of indicating ice age cycles within the layers of a 1620-meter-long ice core. Geologists speculate that jarosite dust could also have accumulated within ice in glaciers on Mars. However, that hypothesis is a matter of controversy because, on Mars, jarosite deposits can be very thick (up to 10 meters). However, Mars is also a very dusty planet and, in the absence of

plate tectonics Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

on Mars, glacial dust deposits might have accumulated over long periods of time.

Use in materials science

Jarosite is also a more generic term denoting an extensive family of compounds of the form AM₃(OH)₆(SO₄)₂, where A⁺ = Na, K, Rb, NH₄, H₃O, Ag, Tl and M³⁺ = Fe, Cr, V. In

condensed matter physics Condensed matter physics is the field of physics that deals with the macroscopic and microscopic physical properties of matter, especially the solid and liquid State of matter, phases, that arise from electromagnetic forces between atoms and elec ...

and

materials science Materials science is an interdisciplinary field of researching and discovering materials. Materials engineering is an engineering field of finding uses for materials in other fields and industries. The intellectual origins of materials sci ...

they are renowned for containing layers with kagome lattice structure, relating to geometrically frustrated magnets.

References

* Palache C., Berman H., and Frondel C. (1951) Dana's system of mineralogy, (7th edition), v. II, 560–562.
Webmineral data

* ttp://news.discovery.com/history/archaeology/mysterious-spheres-emerge-from-ancient-temple-1304291.htm Discovery News (2013) "Robot Finds Mysterious Spheres in Ancient Temple"{{Webarchive, url=https://web.archive.org/web/20150319032519/http://news.discovery.com/history/archaeology/mysterious-spheres-emerge-from-ancient-temple-1304291.htm , date=2015-03-19

External links

Further information about the Jaros Hydrothermal system
Iron(III) minerals Potassium minerals Alunite group Trigonal minerals Minerals in space group 166