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.

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 ...

Cyanotrichite has no twinned crystals known.

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.