Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated phosphates
    Crystal system : Triclinic
    Chemistry : CuFe₆(PO₄)₄(OH)₈ 4H₂O
    Rarity : Very rare

Chalcosiderite is a rare copper and iron phosphate, present in the oxidation zones of polymetallic hydrothermal deposits rich in copper, along with other copper or iron phosphates (dufrenite, libethenite...) often on a matrix of goethite. It forms a series with turquoise, a mineral in which iron is replaced by aluminum. It owes its name to the Greek chalcos (copper) and sidêros (iron) because of its chemical composition. The crystals are short prisms of 3 mm maximum, grouped in bundles or encrustation of a dark green color. It is a mineral only reserved for the collection.

In France, chalcosiderite is known in the tungsten and copper veins of the Montmins, near Echassières (Allier), see main photo.

No fake recorded for this mineral species.