Atacamite

Atacamite from Poona Mine, Moonta, South Australia, Australia, measuring 46 × 38 × 30 mm and weighing 102 grams. This piece represents a copper mineral with a different chemistry from the carbonates so often associated with Australian copper localities. The named mine gives the specimen a useful focus within a collection devoted to the Moonta district.

Atacamite is a copper chloride hydroxide. Chloride is an essential part of its composition, distinguishing it from Malachite, Azurite and the copper oxides. It belongs among the secondary minerals produced through alteration, and illustrates how the chemical components available in fluids can influence which new copper minerals develop within a deposit.

Dark green, finely sparkling mineral development covers much of the face, bordered by more varied turquoise and ochre-toned matrix. The darker centre rewards a close view, where small changes in reflection reveal texture that can be lost in a distant glance. Keeping the outer matrix visible also preserves the contrast that gives the piece its individual appearance. This example comes from the David Vince Collection. Its interest lies in the combination of a specific Moonta locality and a species that broadens the chemical range of a copper-mineral display. Retaining the collection provenance adds the later human story to that geological setting, giving the next owner both the mineral identity and the history that accompanies this individual piece.