Aurichalcite
| Aurichalcite | |
|---|---|
Aurichalcite, 79 Mine, Banner District, Gila County, Arizona, USA
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| General | |
| Category | Carbonate mineral |
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Formula (repeating unit) |
(Zn,Cu)5[(OH)3|CO3]2 |
| Strunz classification | 5.BA.15 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/m |
| Unit cell | a = 13.82, b = 6.419 c = 5.29 [Å] β = 101.04°; Z = 2 |
| Identification | |
| Color | Pale green, greenish blue, sky-blue; colorless to pale blue, pale green in transmitted light |
| Crystal habit | Typically in tufted divergent sprays or spherical aggregates, may be in thick crusts; rarely columnar, laminated or granular |
| Twinning | Observed in X-ray patterns |
| Cleavage | {010} and {100} Perfect |
| Fracture | Uneven |
| Mohs scale hardness | 2 |
| Luster | Pearly, silky |
| Streak | Light blue |
| Diaphaneity | Transparent |
| Specific gravity | 3.96 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.655 nβ = 1.740 nγ = 1.744 |
| Birefringence | 0.0890 |
| Pleochroism | Weak colorless to pale green |
| 2V angle | Measured: 1° to 4°, Calculated: 22° |
| References | |
Aurichalcite is a carbonate mineral, usually found as a secondary mineral in copper and zinc deposits. Its chemical formula is (Zn,Cu)5(CO3)2(OH)6. The zinc to copper ratio is about 5:4.
Aurichalcite typically occurs in the oxidized zone of copper and zinc deposits. Associated minerals include: rosasite, smithsonite, hemimorphite, hydrozincite, malachite and azurite.
It was first described in 1839 by Bottger who named the mineral for its zinc and copper content after the Greek όρειχαλκος, for "mountain brass" or "mountain copper", the name of a fabulous metal. The type locality is the Loktevskoye Mine, Upper Loktevka River, Rudnyi Altai, Altaiskii Krai, Western Siberia, Russia.
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