Azurite
Azurite is a soft, deep-blue copper mineral produced by weathering of copper ore deposits. During the early 19th century, it was also known as chessylite, after the type locality at Chessy-les-Mines near Lyon, France. The mineral, a basic carbonate with the chemical formula Cu3(CO3)2(OH)2, 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. Copper (Cu2+) gives it its blue color.
| Azurite | |
|---|---|
Azurite from New Nevada lode, La Sal, Utah, USA | |
| General | |
| Category | Carbonate mineral |
| Formula (repeating unit) | Cu3(CO3)2(OH)2 |
| IMA symbol | Azu |
| 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, 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 | |
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