Parnauite
| Parnauite | |
|---|---|
Parnauite | |
| General | |
| Category | Arsenate minerals |
| Formula | Cu9(AsO4)2(SO4)(OH)10 · 7H2O |
| IMA symbol | Pna |
| Strunz classification | 8.DF.35 |
| Dana classification | 43.5.13.1 |
| Crystal system | Orthorhombic |
| Unit cell | 641.15 ų (calculated) |
| Identification | |
| Color | Pale blue, green, dark green, blue-green, yellow-green |
| Crystal habit | Fans and rosettes of lath-like crystals; fibrous; scaly crusts |
| Cleavage | Good |
| Mohs scale hardness | 2 |
| Streak | Greenish white |
| Specific gravity | 3.09 |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.680(3), nβ = 1.704(3), nγ = 1.712(3) |
| Birefringence | δ = 0.032 |
| Pleochroism | Weak |
| 2V angle | Measured: 60°(5); calculated: 58° |
| Dispersion | r > v (strong) |
| Extinction | Optic plane parallel to {100}. X = b, Y = a, Z = c. |
| Ultraviolet fluorescence | None |
| Common impurities | P, C, Al |
| References | |
Parnauite is a very rare secondary copper arsenate–sulfate mineral. It forms near the Earth’s surface in oxidized zones of various copper deposits. These copper minerals are altered by oxygen-rich water and new minerals grow as a thin coatings or small crystal clusters. Parnauite is typically blue-green to green and commonly occurs as tiny bladed crystals in fan-shaped sprays or rosettes. It may also appear as scaly crusts or crystal-like surface films.