Tags: Chemical Substance, Mineral.
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 decomposition of pyrite commonly near or in volcanic vents. Occurrences include the Atacama Desert Chile Dresden Saxony Germany San Juan County Utah and Mont Saint-Hilaire Canada. The name is from Latin: halotrichum for salt hair.
