Connellite - Encyclopedia

    Class : Halides
    Subclass : Oxychlorides
    Crystal system : Hexagonal
    Chemistry : Cu19Cl4(SO4)(OH)32 3H2O
    Rarity : Rare

Connellite is a hydrated sulphate from the oxidation zone of copper deposits, it is also present in neoformations in foundry slag. It was named in honor of the Scottish Arthur Connell, professor at the University of St Andrews and who was the first to study it. It appears in tufted or radiated aggregates of fine striated acicular crystals, of a beautiful azure blue to royal blue, sometimes blue-green color.

Main photo : Connellite from Penberthy Croft Mine, St Hilary, Cornwall, England © Steve Rust

Connellite from Gold Hill Mine, Utah, USA © Storm Sears
Connellite from slag of Sitio de  Cobre Mine, Portugal © Pedro Alves
Connellite from Clara Mine, Germany © Jean-Paul Fayard
Connellite from Montroc, Tarn, France © Pascale et Daniel Journet

Connellite in the World

It is a rare secondary mineral, known in magnificent felted aggregates in the mines of English Cornwall, notably Wheal Gorland, near Gwennap, and at Likasi, in Congolese Katanga. Good samples have also been discovered in the surface areas of American copper mines (Bisbee, Majuba Hill, Gold Hill, etc...). It is also reported at the Clara Mine (Germany) and in many other deposits.

Connellite in France

In France, connellite is known at Fontana Rossa, near Ghisoni (Haute-Corse), at Cap Garonne (Var), at Chessy (Rhône), at the Vaulry mines (Haute-Vienne), at the Tistoulet mine (Aude) , in Kaymar and Villefranche-de-Rouergue (Aveyron) and Montroc (Tarn). It has also been reported in the slag of Crozet (Loire) and Poullaouen (Finistère).


No twin known for this mineral species.

Fakes and treatments

No fake identified for this mineral species.

Hardness : 3
Density : 3.36
Fracture : Irregular
Streak : Light blue

TP : Transparent
RI : 1.724 to 1.758
Birefringence : 0.026
Optical character : Uniaxial +
Pleochroism : None
Fluorescence : None

Solubility : Acids and ammonia

Magnetism : None
Radioactivity : None


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