| Ammineite | |
|---|---|
 Sky blue ammineite crystals (a mineral with amine groups, IMA 2008-032) in a matrix of halite. From: Pabellon de Pica, Chanabaya, Iquique Province, Tarapacá Region, Chile. | |
| General | |
| Category | Chloride mineral |
| Formula (repeating unit) | CuCl2(NH3)2 |
| IMA symbol | Amm |
| 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 (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 | |
Ammineite is the first recognized mineral containing ammine groups. Its formula is . The mineral is chemically pure. It was found in a guano deposit in Chile. At the same site other ammine-containing minerals were later found:
- 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
Crystal structure
The characteristic features of the structure of ammineite are:
- layers of trans form of the copper complex, parallel to (001), connected by Cu-Cl bonds
- presence of CuN2Cl4 distorted octahedron ( coordination)
- edge-sharing of the octahedra produce zigzag chains along the direction
- hydrogen bonds between NH3 and Cl atoms
Associated minerals
Ammineite coexists with atacamite, darapskite, halite and salammoniac.
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.
References
- Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ 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