Azurite
| Azurite | |
|---|---|
Azurite with large crystals and light surface weathering. Shilu Mine, Guangdong Province, China
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| General | |
| Category | Carbonate mineral |
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Formula (repeating unit) |
Cu3(CO3)2(OH)2 |
| Strunz classification | 5.BA.05 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/c |
| Unit cell | a = 5.01 Å, b = 5.85 Å c = 10.35 Å; β = 92.43°; Z = 2 |
| Identification | |
| Formula mass | 344.67 g/mol |
| Color | Azure-blue, Berlin blue, very dark to pale blue; pale blue in transmitted light |
| Crystal habit | Massive, prismatic, stalactitic, tabular |
| Twinning | Rare, twin planes {101}, {102} or {001} |
| Cleavage | Perfect on {011}, fair on {100}, poor on {110} |
| Fracture | Conchoidal |
| Tenacity | brittle |
| Mohs scale hardness | 3.5 to 4 |
| Luster | Vitreous |
| Streak | Light blue |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.773 (measured), 3.78 (calculated) |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.730 nβ = 1.758 nγ = 1.838 |
| Birefringence | δ = 0.108 |
| Pleochroism | Visible shades of blue |
| 2V angle | Measured: 68°, calculated: 64° |
| Dispersion | relatively weak |
| References | |
Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. It is also known as Chessylite after the type locality at Chessy-les-Mines near Lyon, France. The mineral, a carbonate, has been known since ancient times, and was mentioned in Pliny the Elder's Natural History under the Greek name kuanos (κυανός: "deep blue," root of English cyan) and the Latin name caeruleum. The blue of azurite is exceptionally deep and clear, and for that reason the mineral has tended to be associated since antiquity with the deep blue color of low-humidity desert and winter skies. The modern English name of the mineral reflects this association, since both azurite and azure are derived via Arabic from the Persian lazhward (لاژورد), an area known for its deposits of another deep blue stone, lapis lazuli ("stone of azure").
Azurite is one of the two basic copper(II) carbonate minerals, the other being bright green malachite. Simple copper carbonate (CuCO3) is not known to exist in nature. Azurite has the formula Cu3(CO3)2(OH)2, with the copper(II) cations linked to two different anions, carbonate and hydroxide. Small crystals of azurite can be produced by rapidly stirring a few drops of copper sulfate solution into a saturated solution of sodium carbonate and allowing the solution to stand overnight.
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Wikipedia