Pickeringite is a

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

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 veins and as secondary mine ...

with formula MgAl₂(SO₄)₄·22(H₂O). It forms a series with

halotrichite Halotrichite, also known as ''feather alum'', is a highly hydrated sulfate of aluminium and iron. Its chemical formula is FeAl2(SO4)4·22H2O. It forms fibrous monoclinic crystals. The crystals are water-soluble. It is formed by the weathering and ...

. It forms as an alteration product of

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 ...

in aluminium rich rocks and in

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when ...

seams. It also occurs in pyrite rich hydrothermal ore deposits in arid regions. It forms in

fumarole A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...

s and in

cave A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...

s. It occurs with

kalinite Kalinite is a mineral composed of hydrated potassium aluminium sulfate (a type of alum). It is a fibrous monoclinic alum, distinct from isometric potassium alum,American Mineralogist (1923) 8:15 named in 1868. Its name comes from ''kalium'' (de ...

, alunogen,

epsomite Epsomite, Epsom salt, or magnesium sulfate heptahydrate, is a hydrous magnesium sulfate mineral with formula MgSO4·7H2O. Epsomite crystallizes in the orthorhombic system as rarely found acicular or fibrous crystals, the normal form is as massiv ...

melanterite Melanterite is a mineral form of hydrous iron(II) sulfate: FeSO4·7H2O. It is the iron analogue of the copper sulfate chalcanthite. It alters to siderotil by loss of water. It is a secondary sulfate mineral which forms from the oxidation of prim ...

, copiapite and

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...

. It was first described in 1844 for an occurrence in Cerros Pintados,

Pampa del Tamarugal Pampa del Tamarugal ("Plateau of the Tamarugal") is a vast plain encompassing a significant portion of the Norte Grande, Chile, and originally named for the ''Prosopis tamarugo'' trees that used to cover its surface. It is located between the par ...

, Iquique Province,

Tarapacá Region The Tarapacá Region ( es, Región de Tarapacá, ) is one of Chile's 16 first-order administrative divisions. It comprises two provinces, Iquique and Tamarugal. It borders the Chilean Arica and Parinacota Region to the north, Bolivia's Orur ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

. It was named for American linguist and philologist John Pickering (1777–1846). Pickeringite

References

Sulfate minerals Monoclinic minerals Minerals in space group 14 {{sulfate-mineral-stub