Lily mine – September 30

The Lily mine is one of very few oxidizied mineral deposits in Peru. The oxidation process at Lily has produced interesting specimens of copper hydroxychlorides, namely atacamite and clinoatacamite. These two species have the same chemistry, Cu2Cl(OH)3, but different atomic arrangements. Once believed to be a polymorph of atacamite, paratacamite requires a minor impurity to stabilize rhombohedral symmetry. Consequently, paratacamite is not a polymorph of atacamite. However, some pseudorhombohedral crystals are known which are very close to the ideal formula, but they actually have monoclinic symmetry. Jambor et al. (1996) named these pseudorhombohedral crystals clinoatacamite. At the Lily mine, clinoatacamite crystals reach 1.3 cm across, a best of species find. Hence, they are the stars of this gallery.

This gallery contains 22 specimens.