PHYSICAL PROPERTIES:
Chemistry: (Zn, Cu)5(OH)6(CO3)2
Composition: Zinc Copper Carbonate Hydroxide
Class: Carbonates
Crystal system: Orthorhombic
Fracture: uneven or fibrous.
Hardness: 2
Specific gravity: 3.5-3.6
Refractive Index:
Luster: pearly
Streak: white to pale shades
Cleavage: perfect in one direction.
Color: Pale greenish blue
Transparency: transparent to translucent.
Associated Minerals: azurite, calcite,
hemimorphite, malachite, limonite, rosasite, and smithsonite.
COMPOSITION:
A basic carbonate of zinc and copper (20.8% CuO, 53.2%
ZnO, 16.1% C02, 9.9% H2O).
DISTINGUISHING CHARACTERISTICS:
The color is usually an attractive grass green to pale green.
But can vary from white to green to greenish blue to light blue. These
soft, pale blue-green scales, which dissolve so easily in acid, are
unlike those of any other mineral . Aurichalcite at times partially
covers red limonite and is associated with such colorful minerals as
azurite, smithsonite, malachite and hemimorphite. Aurichalcite can be
confused with Rosasite, (Cu, Zn)2CO3(OH)2.
Rosasite is usually more massive but not lamellar and Rosasite crystals
are harder than aurichalcite.
ENVIRONMENT:
Secondary, weathered, zone of copper zinc ore deposits.
CRYSTAL DESCRIPTION:Habits
include radiating tufts of acicular crystals and also in encrustation's
of fibrous or lamellar masses.
TESTS:
Infusible on charcoal, but colors the flame green. Soluble
in hydrochloric acid with effervescence, giving green solution, which
turns blue on the addition of ammonia
LOCALITIES:
Good specimens have come from several localities
in Utah, and it is also found in some of the Arizona and New Mexico
copper mines. Mapimi, Durango, Mexico is another well known North American
source. European localities include the famous Lead hills locality (Scotland),
Matlock in Derbyshire, Altai Territory in Russia, Laurium, Greece, Hungary,
Tsumeb, Namibia and Chessy, France.
USES:
It is a very minor ore of zinc and copper when mined
with other minerals. It is primarily used as very nice mineral specimens.
FACTS & HISTORY:
The origin of the name has brought about some debate, since it is
derived from the ancient name for brass. The mineral can be considered
a natural "brass ore," but it's rarity makes it very unlikely, that
it was ever used for this purpose.
Since aurichalcite forms from weathering in ore bodies high in zinc.
It is a good guide to zinc ore.
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