PICKERINGITE

    Class : Sulfates, chromates, molybdates
    Subclass : Hydrated sulfates
    Crystal system : Monoclinic
    Chemistry : MgAl2(SO4)4 22H2O
    Rarity : Quite common

Pickeringite is a highly hydrated sulfate of magnesium and aluminum. It is a fairly widespread mineral which essentially results from the supergene oxidation of sulfides in different contexts rich in aluminum : pyritic hydrothermal deposits, layers of coal with disseminated pyrite, etc... But it is also found in caves, and in hot spring deposits and in some volcanic fumaroles. It was named in honor of the American philosopher John Pickering. Pickeringite forms delicate fibrous to acicular crystals, frequently united in felted, tufted or spherolitic aggregates, encrustations or efflorescences. It is colorless or white, sometimes yellowish or pinkish.

Main photo : Pickeringite from California Rand No. 2 Mine, California, USA © Rock Currier

Pickeringite de Prospect, Australie © Enrico Bonacina
Pickeringite from Vulcano, Aeolian Islands, Italy © Stephan Wolfsried
Pickeringite from Vulcano, Aeolian Islands, Italy © Stephan Wolfsried
Pickeringite from the Wollmersdorf graphite quarry, Austria © Christian Auer
Pickeringite from Cetine, Tuscany, Italy © Jean-Vincent Coureau

Pickeringite in the World

Atacama Desert, in northern Chile (Chuquicamata, Iquique, Quetena), where it is probably formed at the expense of copper sulfides. It is also present in other mines, notably American, German and Austrian. Pickeringite is also reported in Italy, on the island of Elba, and in Terlano.

Phurcalite in France

In France, pickeringite is reported in the fumarolic deposits of Seilhols near Fontanges (Cantal) and in the Avion coal mine near Lens (Pas-de-Calais).

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 1.5
Density : 1.73 to 1.79
Fracture : Conchoidal
Streak : White

TP : Translucent
RI : 1.475 to 1.483
Birefringence : 0.008
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : Water

Magnetism : NoneRadioactivity : None