Conichalcite is a rare secondary mineral from the arsenate class, first described in 1849 by the mineralogist A. Breithaupt and the chemist J. Fritzsche . Translated from Greek conichalcite - "copper lime." Easily soluble in nitric and hydrochloric acids. Conichalcite was also called Higginsitis.
| Conichalcite | |
|---|---|
 Conichalcite spheres on limonite | |
| Formula | CaCu (AsO 4 ) (OH) |
| Impurity | Mg , P , V , Zn |
| Physical properties | |
| Colour | Green, yellow green, yellow |
| Trait color | Light green |
| Shine | Glass, oily |
| Transparency | Translucent, transparent |
| Hardness | 4 - 5 |
| Cleavage | Missing |
| Kink | Uneven |
| Density | 4.33 g / cmΒ³ |
| Syngonia | Rhombic (orthorhombic) |
| Refractive index | nΞ± = 1,778 - 1,800 nΞ² = 1,795 - 1,831 nΞ³ = 1,801 - 1,846 |
Content
Crystallography
Point group - 2 2 2 - Dipyramidal
Space group - P21 21 21
Syngonia - Rhombic (orthorhombic)
Cell parameters - a = 7.39 (1) Γ , b = 9.23 (1) Γ , c = 5.83 (1) Γ
The ratio a: b: c = 0.801: 1: 0.632
The number of formula units (Z) - 4
Unit cell volume - V 397.66 Γ Β³ (calculated by unit cell parameters)
Twin - By {001} rarely.
Selection Forms
Most often, conichalcite stands out in the form of cluster-like, roundish and kidney-shaped masses. Rarely, conichalcite can stand out in the form of small crystals in the form of a short and flat prism.
In association with other minerals
Conichalcite is associated with the minerals of copper , iron and zinc . Such minerals include: limonite , malachite , smitsonite , adamine and olivenite .
Chemical Composition
Calcium - 15.44% (in the form of oxide - 21.61%), copper - 24.48% (in the form of CuO - 30.65%), arsenic - 28.87% (in the form of oxide - 44.28%) hydrogen - 0.39% (in the form of oxide - 3.47%), oxygen - 30.82%.
In the role of pigment
Low-quality samples of conichalcite are raw materials for the production of natural pigments. The raw materials go through a long cleaning process. The result is a fine powder that mixes with the liquid base. The green pigment from conichalcite is called Verona Greens or Schweinfurt Greens.
Deposits
Deposits of conichalcite are few. The best samples are mined in Mapimi ( Mexico ), Tsumebe ( Namibia ) and the DRC .
Literature
- Breithaupt and Fritzsche (1849) Annalen der Physik, Halle, Leipzig: 77: 139 (as Konichalcit).
- Fritzsche (1849) Annalen der Physik, Halle, Leipzig: 77: 180.
- Hillebrand (1883) Proceedings of the Colorado Science Society: 1: 114.
- Reddy, BJ; Frost, RL; Martens, WN (2005): Characterization of conichalcite by SEM, FTIR, Raman and electronic reflectance spectroscopy. Mineralogical Magazine 69, 155-168.