Ammineite
Ammineite is the first recognized mineral containing ammine groups. Its formula is [CuCl2(NH3)2]. The mineral is chemically pure. It was found in a guano deposit in Chile.[1][2] At the same site other ammine-containing minerals were later found:[3] [4][5][6]
- Chanabayaite, CuCl(N3C2H2)(NH3)·0.25H2O (an alternative formula), a triazolate mineral
- Joanneumite, Cu(C3N3O3H2)2(NH3)2, an isocyanurate mineral
- Shilovite, Cu(NH3)4(NO3)2
| Ammineite | |
|---|---|
 | |
| General | |
| Category | Chloride mineral |
| Formula (repeating unit) | CuCl2(NH3)2 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Cmcm |
| Unit cell | a = 7.79, b = 10.64 c = 5.84 [Å] (approximated) |
| Identification | |
| Color | Blue |
| Crystal habit | Hypidiomorphic crystals; powdery masses |
| Mohs scale hardness | 1 |
| Luster | Vitreous |
| Streak | Light blue |
| Specific gravity | 2.38 (calculated) |
| Pleochroism | Dark blue to light blue |
| References | [1][2] |
Crystal structure
The characteristic features of the structure of ammineite are:[1]
- layers of trans form of the copper complex, parallel to (001), connected by Cu-Cl bonds
- presence of CuN2Cl4 distorted octahedron ([4+2] coordination)
- edge-sharing of the octahedra produce zigzag chains along the [001] direction
- hydrogen bonds between NH3 and Cl atoms
Associated minerals
Ammineite coexists with atacamite, darapskite, halite and salammoniac.[1]
Origin
Ammineite is supposed to be a result of an interaction of an earlier copper mineral, likely from a plutonic rock, with ammonia in guano. Ammonia may be produced in decomposition of compounds like urea or uric acid.[1]
References
- Bojar, H.-P., Walter, F., Baumgartner, J., and Färber, G. 2010. Ammineite, CuCl2(NH3)2, a new species containing an ammine complex: mineral data and crystal structure. The Canadian Mineralogist 48(6), 1359-1371.
- Mindat, Ammineite, http://www.mindat.org/min-38895.html
- Mindat, Pabellón de Pica, http://www.mindat.org/loc-192704.html
- Mindat, Chanabayaite, http://www.mindat.org/min-43945.html
- Mindat, Joanneumite, http://www.mindat.org/min-42755.html
- Mindat, Shilovite, http://www.mindat.org/min-46139.html
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