Chrysocolla
| Chrysocolla | |
|---|---|
 Chrysocolla from Australia | |
| General | |
| Category | Silicate mineral |
| Formula (repeating unit) | (Cu,Al)2H2Si2O5(OH)4·nH2O |
| Strunz classification | 9.ED.20 |
| Crystal system | Orthorhombic |
| Unit cell | a = 5.7 Å, b = 8.9 Å, c = 6.7 Å |
| Identification | |
| Color | Blue, blue-green, green |
| Crystal habit | Massive, nodular, botryoidal |
| Cleavage | none |
| Fracture | Irregular/uneven, sub-conchoidal |
| Tenacity | Brittle to sectile |
| Mohs scale hardness | 2.5 - 3.5 |
| Luster | Vitreous to dull |
| Streak | white to a blue-green color |
| Diaphaneity | Translucent to opaque |
| Specific gravity | 1.9 - 2.4 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.575 - 1.585 nβ = 1.597 nγ = 1.598 - 1.635 |
| Birefringence | δ = 0.023 - 0.050 |
| References | [1][2][3] |
Chrysocolla is a hydrated copper silicate mineral with formula (Cu,Al)2H2Si2O5(OH)4·nH2O.
Properties
Chrysocolla has a blue-green color and is a minor ore of copper, having a hardness of 2.5 to 3.5.
Name and discovery
The name comes from the Greek chrysos, "gold", and kolla, "glue", in allusion to the name of the material used to solder gold, and was first used by Theophrastus in 315 BCE.
Formation and occurrence
It is of secondary origin and forms in the oxidation zones of copper ore bodies. Associated minerals are quartz, limonite, azurite, malachite, cuprite, and other secondary copper minerals.
It is typically found as botryoidal or rounded masses and crusts, or vein fillings. Because of its light color, it is sometimes confused with turquoise.
Notable occurrences include Israel, Democratic Republic of Congo, Chile, Cornwall in England, and Arizona, Utah, New Mexico and Pennsylvania in the United States.
References
