Cornetite is a rare secondary copper phosphate found in the oxidation zone of copper deposits. This is a dramatic, really rich and large specimen for this material and is from a small new find at the Star of the Congo Mine. A thin crust of sparkly, teal-blue cornetite, in botryoidal form, covers pretty chrysocolla lining a large vug in gossan matrix. This is from a find made in mid-2009.