MINIUM

    Class : Oxides and hydroxides
    Subclass : Oxides
    Crystal system : Tetragonal
    Chemistry : Pb3O4
    Rarity : Uncommon

Minium is a secondary lead mineral formed by oxidation of galena or transformation of cerussite. It is uncommon due to its very specific formation conditions, which require both an alkaline environment and a dry, desert to semi-desert climate. It is a mineral known since Antiquity that is also found in industrial slag. The term minium originally designated cinnabar, often associated with red lead oxide. It is an opaque mineral with a dull luster which always occurs in earthy crusts or powdery masses of typical bright red color passing to brownish red, sprinkling galena or cerussite. It is locally an important lead ore.

Main photo : Minium from Broken Hill, Australia © Rob Lavinsky

Minium from Tsumeb, Namibia © Paul de Bondt
Cerussite pseudomorph after minium from Tonopah-Belmont Mine, Arizona, USA © Van King
Minium from Chah Milleh Mine, Anarak, Iran © Tony Peterson
Minium from St-Prix, Autun, Saône-et-Loire, France © Alain Tuel

Minium in the World

Minium is mainly known in gossans of lead deposits in dry climates: Iran (Anarak), Mexico (Zimapan), Namibia (Tsumeb), Australia (Broken Hill). It constituted a significant part of the lead ore in Leadville (Colorado).

Minium in France

In France, minium is known as a dusting in the lead deposits of Molérats (Saône-et-Loire) and St-Avold (Moselle), as well as in the lead and antimony mine of Ally (Haute-Loire). It is also reported in Asprières (Aveyron) and in the slag of Poullaouen (Finistère).

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 2.5
Density : 8.9 to 9.2
Fracture : Undetermined
Streak : Yellow-orange

TP : Opaque to translucent
RI : 2.410 to 2.420
Birefringence : 0.010
Optical character : Uniaxial
Pleochroism : Strong
Fluorescence : None

Solubility : Hydrochloric acid

Magnetism : NoneRadioactivity : None