Cyanotrichite - Encyclopedia

    Class : Sulphates, chromates, molybdates
    Subclass : Hydrated sulphates
    Crystal system : Orthorhombic
    Chemistry : Cu4Al2(SO4)(OH)12 . 2H2O
    Rarity : Rare


Cyanotrichite is a secondary mineral of the oxidation zone of copper deposits. Its genesis seems facilitated by an acid environment and a clayey surrounding. It owes its name to the Greek kuanos (blue) and thrix (hair) in connection with its color and its habit in tufts of acicular crystals. It comes in orthorhombic fibers assembled in radiate rosettes, urchins with velvety aspect and silky luster. Its sky blue to azure blue color and its pale blue streak are characteristic as well as its association with other arsenates and sulphates of copper (chalcophyllite, spangolite, brochantite, adamite, etc...). It is a mineral little known to collectors who has no particular use.

Cyanotrichite in the World

Among the world's most beautiful occurrences for this species, we can cite Qinglong Mine, Guizhou Province, China (main photo) and Arizona copper mines, mainly from Grandview where cyanotrichite forms magnificent spherulitic aggregates and tufts of crystals. This mineral is also present in Romania (Moldawa), in Greece in the Laurion mines, in Majuba Hill (Nevada). It is also found in felts of pale blue needle-shaped crystals at the La Vieja mine (Atacama Desert, Chile).
Beautiful cyanotrichite urchins from Qinglong, Guizhou, China
Beautiful cyanotrichite urchins from Qinglong, Guizhou, China
Beautiful cyanotrichite urchins from Qinglong, Guizhou, China
Beautiful cyanotrichite urchins from Qinglong, Guizhou, China

Cyanotrichite in France

In France is among the best specimens worldwide for the species at the Cap Garonne mine (Var), with acicular crystals that can exceed 15 mm grouped fibrin-bound aggregates. It is found in microcrystals in many deposits such as : Port Brûlé (Nièvre), Treille Mine (Haut-Rhin), Tistoulet and Salsigne Mines (Aude), Couloumier Mine (Ariège), La Fage and La Baume (Aveyron), Valcroze (Gard), La Moutoune (Hérault), St. Lucie mine (Lozère), Mas Vicenç (Pyrénées-Orientales), etc ...

Twinning

Cyanotrichite has no twinned crystals known.

Fakes and treatments

No scam known for this mineral. An anionic CO3 group can be associated with the SO4 group to form carbonate-cyanotrichite, a mineral species close to cyanotrichite, belonging according to the authors to carbonates or sulfates. It can easily be confused with the latter.



Hardness : 1 to 3
Density : 2.76
Fracture : Undetermined
Trace : Blue



TP : Translucent to transparent
RI : 1.588 to 1.6554
Birefringence : 0.067
Optical character : Biaxial +
Pleochroism : Weak
Fluorescence : None


Solubility : All acids

Magnetism : None
Radioactivity : None

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