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Aurichalcite has a beautiful pastel color that is very distinctive. In its most typical form, the tiny fragile crystal needles may rub off when touched, and will often leave a blue residue on a surface. Handling of such specimens should be avoided due to their fragility, and washing Aurichalcite should also be avoided for this reason.
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Chemical Formula |
(Zn,Cu)5(CO3)2(OH)6 |
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Composition |
Basic carbonate of zinc and copper. (The ratio of zinc to copper is about 5:2) |
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Color |
Light blue, sky blue, blue-green, pale green |
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Streak |
Pale blue-green to white |
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Hardness |
2 |
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Crystal System |
Orthorhombic |
Crystal Forms
and Aggregates |
Most often as a mat of tiny, thin, interwoven needles. Also plumose, as crusts, as thin scales, radiating, botryoidal, and as tiny balls of radiating crystals. Individual crystals, which are very small, are usually elongated, and occasionally tabular. |
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Transparency |
Translucent |
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Specific Gravity |
3.6 - 4.2 |
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Luster |
Silky to pearly |
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Cleavage |
Indiscernible |
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Fracture |
Uneven |
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Tenacity |
Slightly flexible and sectile |
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Complex Tests |
Effervesces in dilute hydrochloric acid |
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In Group |
Carbonates; |
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Striking Features |
Color, crystal habits, fragility, and occurrences |
| Environment |
As a secondary mineral in the oxidation zone of zinc and copper sulfide deposits. |
| Rock Type |
Sedimentary, Metamorphic |
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Popularity (1-4)
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3 |
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Prevalence (1-3)
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3 |
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Demand (1-3) |
2 |
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Aurichalcite is considered a natural brass ore, since it is composed of zinc and copper, the constituents of brass. However, it occurs too sparingly, and there are no practical methods for brass to be extracted from it. It is, though, an ore of zinc and copper when found in mines where there exists workable deposits of these elements.
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Aurichalcite comes from many of the classic European copper oxidation deposits. These include Chessy, France; Laurium, Greece; the Leadhills of Scotland; and Matlock, Derbyshire and Caldbeck Fells, Cumbria, England. Other European occurrences include Campiglia Marittima, Livorno Province, Tuscany, Italy; and the Rohdenhaus Quarry, Wolfrath, North Rhine-Westphalia, Germany.
Perhaps the best-known Aurichalcite locality is the Ojuela Mine, Mapimi, Durango, Mexico, where it occurs in vibrant acicular tufts, associated with Hemimorphite and Adamite on a brown Limonite matrix. Also from the Ojuela Mine are highly attractive rhombic Calcite crystals with dense, internal inclusions of brightly-colored Aurichalcite.
In the U.S., good Aurichalcite specimens have come primarily from Arizona, at the 79 Mine in Hayden, Gila Co.; the Copper Queen Mine in Bisbee, Cochise Co.; and from the Silver Hill Mine in Pima Co. Other important localities include Magdalena, Soccoro Co., New Mexico; the Hidden Treasure Mine and Stockton, Tooele Co., Utah; and the Keeler Mine, Cottonwood Canyon, Salt Lake Co., Utah. Aurichalcite has also been found in the Grand Deposit Mine of White Pine Co., Nevada; the Darwin District of Inyo Co., California; and the Tin Mountain Mine, Custer Co., South Dakota.
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Malachite - Greener color, usually more compact.
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