Halotrichite, also known as ''feather alum'', is a highly hydrated sulfate of

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 ...

and

iron Iron () is a chemical element with symbol Fe (from la, ferrum) 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, right in ...

. 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 decomposition 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 ...

commonly near or in

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plat ...

vents. The locations of natural occurrences include: the

Atacama Desert The Atacama Desert ( es, Desierto de Atacama) is a desert plateau in South America covering a 1,600 km (990 mi) strip of land on the Pacific coast, west of the Andes Mountains. The Atacama Desert is the driest nonpolar desert in th ...

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 ...

;

Dresden Dresden (, ; Upper Saxon: ''Dräsdn''; wen, label= Upper Sorbian, Drježdźany) is the capital city of the German state of Saxony and its second most populous city, after Leipzig. It is the 12th most populous city of Germany, the fourth ...

Saxony Saxony (german: Sachsen ; Upper Saxon German, Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a ...

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 ...

;

San Juan County, Utah San Juan County ( ) is a county in the southeastern portion of the U.S. state of Utah. As of the 2010 United States Census, the population was 14,746. Its county seat is Monticello, while its most populous city is Blanding. The Utah State ...

;

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its ...

and Mont Saint-Hilaire,

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...

. The name is from

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

: ''halotrichum'' for salt hair which accurately describes the

precipitate In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean ...

mineral. ;Gallery File:Halotrichite Hydrous iron aluminum sulfate Corral, California 3009.jpg, Halotrichite from

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

File:Halotrichite-179634.jpg, Halotrichite from the abandoned Golden Queen mine on Soledad Mountain south of

Mojave, California Mojave (formerly Mohave) is an unincorporated community in Kern County, California, United States. Mojave is located east of Bakersfield, and north of Los Angeles, at an elevation of . The town is located in the western region of the Mojav ...

References

Saint-Hilaire
Iron(II) minerals Aluminium minerals Sulfate minerals Monoclinic minerals Minerals in space group 14 {{sulfate-mineral-stub