CHALCOPHANITE

    Class : Oxides and hydroxides
    Subclass : Hydroxides and hydrates
    Crystal system : Trigonal
    Chemistry : ZnMn3O7 3H2O
    Rarity : Quite common

Chalcophanite is a secondary mineral of the supergene oxidation zone of zinc and manganese deposits, where it accompanies various oxides of zinc, manganese and iron. Its name comes from the Greek khalcos and phainein (to appear) which reveals the particularity of this mineral to change color under the effect of heat (from black to coppery bronze). It occurs in small tabular or lamellar crystals commonly pseudo-octahedral, not exceeding 8 mm, in geodic botryoidal masses, or in stalactitic aggregates. It is a bluish to iron-black mineral. It is an accessory manganese ore.

Main photo : Chalcophanite from Torgal Mine, Portugal © Pedro Alves

Chalcophanite from Torgal Mine, Portugal © Pedro Alves
Chalcophanite from Gold Hill Mine, Utah © Alex Earl
Chalcophanite from Herdade dos Pendões, Portugal © Pedro Alves
Chalcophanite from Peyrebrune, Tarn, France © Georges Favreau (SEM image)

Chalcophanite in the World

The finest known samples were discovered at the Ojuela mine, near Mapimi (Mexico), but good quality specimens come from the deposits of Franklin and Sterling Hill (New Jersey), and Tamera (Tunisia). The large manganese district of Hotazel (South Africa) also yielded good samples of this relatively common mineral.

Chalcophanite in France

In France, chalcophanite is reported at Peyrebrune (Tarn) as well as at the Batère mine (Pyrénées-Orientales).

Twinning and special crystallizations

No twin known for this mineral species.

Fakes and treatments

No fakes identified for this mineral species but very easy to confuse with hematite, pyrolusite or goethite without chemical analysis...


Hardness : 2 to 2.5
Density : 3.35
Fracture : Conchoidal
Streak : Blue

TP : Translucent to transparent
RI : 1.712 to 1.732
Birefringence : 0.020
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : Acids


Magnetism : None
Radioactivity : None

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