Acid, Basic and Hydrous Carbonates – Malachite, Green Copper Carbonate

Malachite. Green Copper Carbonate
Composition. Basic carbonate of copper, (Cu. OH) ₂ CO₃ or CuCO₃.Cu (OH) ₂= Carbon dioxide 19.9, cupric oxide 71.9 water 8.2. Copper = 57.4.

Crystallization. Monoclinic. Crystals usually slender prismatic but seldom distinct.

Structure. Usually radiating fibrous with botryoidal or stal-actitic structure. Often granular or earthy.

Physical Properties. Perfect basal cleavage. H. = 3.5-4. G. =3.9-4.03. Adamantine to vitreous luster in crystals; often silky in fibrous varieties; dull in earthy type. Color bright green. Translucent to opaque.

Tests. Fusible (3), giving a green flame. With fluxes in R.F. on charcoal gives copper globule. Soluble in hydrochloric acid with effervescence. Solution turns deep blue with excess of ammonia. Much water in C.T. Recognized by its bright green color and radiating fibrous structure.

Occurrence. An important and widely distributed copper ore of secondary origin. Found in the oxidized portions of copper veins associated with azurite, cuprite, native copper, iron oxides and the various suphides of copper and iron. Usually occurs in cooper veins that lie in limestones. Notable localities for its occurrence are at Nizhne Tagilsk in the Ural Mountains; at Chessy, near Lyons, France, associated with azurite; form near Otavi, South West Africa; from Rhodesia; South Australia; etc. In the United States, an important copper ore in the southwestern copper districts; at Bisbee, Morenci, and other localities in Arizona; in New Mexico.

Name. Derived from the Greek word for mallows, allusion to its green color.

Use. An important ore of copper. Has been used to some extent as an ornamental material for vases, veneer for table tops, etc.