|
Halotrichite |
Chemical Formula |
FeAl2(SO4)4·22H2O. |
Species |
Sulfates |
Crystal System |
Monoclinic |
Mohs Scale |
1-2 |
Specific Gravity |
1.89 |
Color |
colourless to white, yellowish, greenish |
Luster |
vitreous |
Diaphaneity |
transparent, translucent |
Cleavage |
poor/indistinct |
Fracture |
conchoidal |
Halotrichite, also known as
feather alum, is a highly hydrated sulfate of aluminium and iron. It is formed by the weathering and decomposition of pyrite commonly near or in volcanic vents. Its chemical formula is FeAl
2(SO
4)
4·22H
2O. It forms fibrous monoclinic crystals. The crystals are water soluble. 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.