PARATACAMITE

    Class : Halides
    Subclass : Oxychlorides
    Crystal system : Trigonal
    Chemistry : Cu2Cl(OH)3
    Rarity : Rare

Paratacamite is an alteration mineral from copper deposits occurring in arid and saline conditions. More rarely it is a mineral from fumarolic deposits or an alteration product of the underwater sulfides of black smokers. It has three polymorphs: botallackite, clinoatacamite and atacamite. Its name comes from the Greek para (near) and its dimorphic relationship with atacamite. Paratacamite occurs in rhombohedral crystals, commonly twinned, in masses, in powdery encrustations, sometimes fibrous and spherolitic in appearance. Like atacamite, paratacamite has a bright luster, and an emerald green to blackish green, rarely light green color.

Main photo : Paratacamite from La Vendida Mine, Chile © Matteo Chinellato

Paratacamite and cerussite from Mina Santa Barbara, San José, Spain © Juan Miguel Segura
Paratacamite from Botallack Mine, Cornwall, England © Steve Rust
Paratacamite from Lily Mine, Humay District, Peru © Italo Campostrini
Paratacamite from Amelia Mine, Boleo, Mexico © Rob Lavinsky

Paratacamite in the World

The main deposits of paratacamite are those in the Atacama Desert (Chile) which have provided very beautiful specimens. The largest crystals appear to come from mines in Arizona, notably Bisbee and Mammoth St-Antony which yielded 1.5 cm crystals. Australian deposits, notably Nangaroo, near Murrin-Murrin, also provide very beautiful crystals. Paratacamite is quite common in the copper veins of English Cornwall (Botallack, Levant, etc...), and in the fumarolic deposits of Vesuvius.

Paratacamite in France

In France, paratacamite is present in the copper vein of Aber, near Crozon (Finistère) as well as at Cap Garonne (Var).

Twinning

Twins on {10-11} are common, sometimes polysynthetic.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 3
Density : 3.72 to 3.74
Fracture : Irregular to conchoidal
Streak : Green

TP : Translucent to opaque
RI : 1.826 to 1.837
Birefringence : 0.007
Optical character : Uniaxial -
Pleochroism : Low
Fluorescence : None

Solubility : Acids

Magnetism : NoneRadioactivity : None