PLUMBOJAROSITE

    Class : Sulfates, chromates, molybdates
    Subclass : Anhydrous sulfates
    Crystal system : Trigonal
    Chemistry : PbFe6(SO4)4(OH)12
    Rarity : Quite common

Plumbojarosite belongs to the alunite group. It is a secondary mineral common in the oxidation zone of lead deposits in arid climates. Its name comes from the Latin plumbum (lead) and the mineral jarosite. Plumbojarosite occurs in coatings, encrustations and earthy masses of yellow to ocher brown, made up of microscopic crystals in hexagonal tablets or in pseudo-octahedra, with a smooth feel, often difficult to distinguish from iron oxides. It is an accessory of lead ore.

Main photo : Plumbojarosite from Elba Island, Italy © Jean-Vincent Coureau

Plumbojarosite in the World

Plumbojarosite was sometimes encountered in quantities exploitable for lead, as in Bolkardag (Anatolia, Turkey). It is also widespread in the oxidation zone of the American West, particularly in the Tombstone district, where the Toughnut Mine yielded the best known specimens.

Plumbojarosite in France

In France, plumbojarosite is known in sub-millimeter crystals in the Rabasse polymetallic deposit (Hérault), but also at the Rhun mine (Côtes-d'Armor), at Chaillac (Indre) and at St-Laurent-le-Minier (Gard).

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 1.5 to 2
Density : 3.67
Fracture : Micaceous
Streak : Pale yellow

TP : Translucent to opaque
RI : 1.783 to 1.878
Birefringence : 0.095
Optical character : Uniaxial -
Pleochroism : Brown-yellow
Fluorescence : None

Solubility : Acids

Magnetism : NoneRadioactivity : None