Aluminite - Encyclopedia

    Class : Sulphates, chromates, molybdates
    Subclass : Hydrated sulfates
    Crystal System : Monoclinic
    Chemistry : Al2(SO4)(OH)4 7H2O
    Rarity : Uncommon

Aluminite is a recently formed hydrated aluminum sulphate observed in clayey environments, in maerls and lignites. It is an infrequent mineral which is formed by the action of sulphated solutions deriving from the oxidation of sulfides (pyrite) on alumina silicates. It is its name to its chemical composition. It presents as reniform or nodular masses, sometimes spherolitic, made up of tiny fibers, white to pale greyish-green or pale pink-orange in color.

Aluminite in the World

Aluminite is known in large concretions in the chalks of New Haven in Sussex, England (main photo © Rob Lavinsky), and in small capillary crystals in Matatiele (South Africa). It is also known from Vesuvius (Italy), Halle (Germany, where it was first described) and several American sites.

Aluminite in France

In France, aluminite is described in Auteuil and in the quarries of Issy, near Paris, in Epernay (Marne) as well as in Huelgoat (Finistère).

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes reported for this mineral species.


Hardness : 1 to 2
Density : 1,7
Fracture : Irregular
Trace : White


TP : Translucent to opaque
RI : 1.459 to 1.470
Birefringence : 0,011
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None

Solubility : Nitric acid and hydrochloric acid

Magnetism : None
Radioactivity : None