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. 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 ([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.

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.