Azurite
| Azurite | |
|---|---|
Azurite from New Nevada lode, La Sal, Utah, United States | |
| General | |
| Category | Carbonate mineral |
| Formula | 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 | |
Azurite or Azure spar 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 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 deep blue color.