Pickeringite
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Pickeringite is a magnesium aluminium sulfate mineral with formula MgAl24·22. It forms a series with halotrichite.
Cobalt rich pickeringite from the Northern Slanské Mts, Prešov Region, Slovakia
Pickeringite in the Natural History Museum
Halotrichite
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Halotrichite, also known as feather alum, is a highly hydrated sulfate of aluminium and iron. Its chemical formula is FeAl24·22H2O. It forms fibrous monoclinic crystals. The crystals are water-soluble
A sample of halotrichite
Halotrichite from California
Halotrichite from the abandoned Golden Queen mine on Soledad Mountain south of Mojave, California