Antlerite

The Chuquicamata District in the Antofagasta Region of Chile has over 140 recorded mineral species, many of which are rare and it is the type locality to 22 species.  This medium cabinet-sized specimen of deep emerald-green Antlerite densely coats the flat fractured surface of a creamy-white, heavily altered porphyritic matrix.  The Antlerite, a hydrous copper sulphate, forms tabular crystals to about 4 x 4 mm lying flat against the matrix and where areas of broken crystals occur, due to contact damage with the opposite face of the in-situ fracture surface, the Antlerite forms a lighter, spring-green patchwork.  About two thirds of the fracture plane is coated with a 1.5 mm deep solid layer of dark bottle-green Antlerite.  A rich specimen of this relatively rare sulphate.