Melaconite

Melaconite is a mineral consisting of cupric oxide, CuO. It is known also as black copper ore. In appearance it is strikingly different from cuprite or red copper ore, which is cuprous oxide.

Crystals are rare; they belong to the monoclinic, or possibly to the anorthic system, and have the form of thin triangular or hexagonal scales with a steel-grey color and brilliant metallic lustre. More often, the mineral is massive, earthy or pulverulent, and has a dull iron-black color. Hence the name melaconite, from the Greek μέλας, black and, κόνις, dust, which was originally given by F. S. Beudant in 1832 in the form melaconise.

The crystallized Vesuvian mineral was later named tenorite, a name commonly adopted for the species. The hardness of the crystals is 3.4, but the earthy and powdery forms readily soil the fingers; the specific gravity is 5.9.

Crystals have been found only at Mt Vesuvius, where they encrust lava, and in Cornwall. The other forms of the mineral, however, are common in copper mines, and have resulted by the alteration of chalcocite, chalcopyrite and other copper ores, on which they often form a superficial coating.

References

•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.