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
CategoryChloride mineral
Formula
(repeating unit)
CuCl2(NH3)2
IMA symbolAmm[1]
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupCmcm
Unit cella = 7.79, b = 10.64
c = 5.84 [Å] (approximated)
Identification
ColorBlue
Crystal habitHypidiomorphic crystals; powdery masses
Mohs scale hardness1
LusterVitreous
StreakLight blue
Specific gravity2.38 (calculated)
PleochroismDark blue to light blue
References[2][3]

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.[2][3] At the same site other ammine-containing minerals were later found:[4][5][6][7]

Crystal structure

The characteristic features of the structure of ammineite are:[2]

  • 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.[2]

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.[2]

References

  1. 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.
  2. 1 2 3 4 5 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.
  3. 1 2 Mindat, Ammineite, http://www.mindat.org/min-38895.html
  4. Mindat, Pabellón de Pica, http://www.mindat.org/loc-192704.html
  5. Mindat, Chanabayaite, http://www.mindat.org/min-43945.html
  6. Mindat, Joanneumite, http://www.mindat.org/min-42755.html
  7. Mindat, Shilovite, http://www.mindat.org/min-46139.html
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