Langite - Encyclopedia

    Class : Sulfates, chromates, molybdates
    Subclass : Hydrated sulfates
    Crystal system : Orthorhombic
    Chemistry : Cu4(SO4)(OH)6 2H2O
    Rarity : Rare

Langite is a rare secondary sulfate typical of the oxidation zone of copper deposits, dimorphic from wroewolfeite. It is also found in certain industrial slags. It was named in honor of Victor von Lang, physicist and crystallographer, Professor at the University of Vienna in Austria. Langite is rare in well-formed equant or prismatic crystals and commonly occurs in crystalline aggregates or scaly masses forming sky blue to greenish blue encrustations.

Main photo : Langite from Podlipa deposit, Lubietová, Slovakia © Stephan Wolfsried

Twinned langite from Podlipa deposit, Lubietová, Slovakia © Martin Reich
Twinned langite from Clara Mine, Oberwolfach, Germany © Michael Förch
Langite from Katharina I Mine, Germany © Edgar Müller
Twinned langite of Franciman, Tarn, France © Jean-Claude Dol

Langite in the World

Large crystals of 5 mm are known from the copper mines of St-Blazey and St-Just in English Cornwall. Langite crystals have also been discovered in other superficial areas of copper deposits, notably in several American sites, in Slovakia and in Ireland (Casteltown Bearhaven, County Cork) where it forms spectacular wavelet concretions.

Langite in France

In France, langite is known in the oxidation zone of several small chalcopyrite veins, notably at St-Rome-du-Tarn (Aveyron), which yielded very beautiful 5 mm crystals implanted on barite, among the largest known for this species. It is also reported in Longefay and Chessy (Rhône), in Franciman and Montroc (Tarn), in Villefranche-de-Rouergue and in Kaymar (Aveyron), in Ste-Marie-aux-Mines and Steinbach (Haut-Rhin), at the Tistoulet Mine (Aude), at Maxonchamp and Faymont (Vosges), at St-Laurent-le-Minier (Gard), at Lachaux (Puy-de-Dôme) and in the slags of Crozet (Loire) and Poullaouen (Finistère).

Twinning

Twins on {110} are common, and can be repeated to form stars or pseudo-hexagonal crystals.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 2.5 to 3
Density : 3.5
Fracture : Undeterminated
Streak : Blue

TP : Translucent to transparent
RI : 1.708 to 1.798
Birefringence : 0.090
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : Hydrochloric acid, ammonia

Magnetism : NoneRadioactivity : None

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