Chalcophyllite - Encyclopedia

    Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated arsenates
    Crystal system : Trigonal
    Chemistry : Cu₁₈Al₂(AsO₄)₄(SO₄)₃(OH)₂₄. 36H₂O
    Rarity : Uncommon to rare

Chalcophyllite is a secondary arseniosulphate of the oxidation zone of copper deposits. Its name is derived from the Greek khalkos (copper) and phullon (leaf) which emphasizes both its chemical composition and its structure. The crystals are very flattened rhombohedra with a perfect cleavage on {0001}, as for the micas, with faces sometimes striated in the 3 directions ; their habit is frequently hexagonal in appearance. Chalcophyllite also occurs in flaky aggregates, leaf masses and rosettes. Its emerald green to bluish green color, associated with a subadamantine luster is characteristic. It is a mineral that has no particular use, its crystals are only intended for the mineral collection.

In France, superb millimeter-scale crystals associated with cyanotrichite were extracted from the Cap Garonne mine (Var). It is also still found in micro-crystals at Echassières (Allier), at the Mine de la Treille and Sankt Johann (Haut-Rhin) and at Faymont (Vosges). In Salsigne (Aude), crystals can reach half a centimeter.

Chalcophyllite can be twinned on {10-10}, but this is hardly visible.

No falke recorded for this mineral species.