An unusually large and rich cabinet specimen from this important historic copper deposit. This is a two-sided specimen featuring different occurrences and crystal aggregates. The "top" of the piece features swarms of lustrous, deep-green CRYSTALS of Antlerite up to 3.5mm! Crystal aggregates are loose to tightly grouped and are incredibly dense on one side of the piece. The "bottom" of the specimen is completely different: vitreous, translucent to transparent, dark emerald green crystals are isolated or occur in loose groups. Unaided or with a loupe, orthorhombic bi-pyramidal crystals are readily discernible. Antlerite is an uncommon copper sulfate hydroxide that forms in the oxidation zone of porphyry copper deposits in arid climates, like the Atacama Desert of northern Chile where this copper deposit is located. This open pit copper mine is now defunct and important specimens are becoming harder to find. Cabinet-sized pieces of this caliber are simply unobtainable now. This is a very fine example of the species that features abundant, quality crystals on a museum sized matrix!