Azurite | |
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General | |
Category | Carbonate mineral |
Formula (repeating unit) | Cu3(CO3)2(OH)2 |
IMA symbol | Azu[1] |
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 | [2][3][4] |
Azurite or Azure spar[5]: 14 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.[3] 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.[6] Copper (Cu2+) gives it its blue color.[7]