|
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; colourless in transmitted light. |
Luster |
Vitreous |
Refractive Index |
n = 1.480 n = 1.486 n = 1.490 |
Diaphaneity |
Transparent, Translucent |
Cleavage |
Poor/IndistinctOn , poor. |
Fracture |
Conchoidal |
Crystal Habit:Crystals acicular ; distinctly terminated crystals rare. Radial or matted aggregates of hair-like crystals; tufted; spheroidal; as incrustations or effloresences; asbestiform. Larger crystals may be hollow or contain bubbles of liquid or gas. |
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 FeAl2(SO4)4·22H2O.
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.