I have worked in copper and brass mills all my life and have never seen green oxides of copper. Cuprous oxide (Cu2O) which forms at low temperatures is reddish -brown and cupric oxide (CuO) that forms at higher temperatures is black and often scaly. Black Cupric Oxide is removed with dilute sulfuric acid. read more
malachite, the green, hydrated copper carbonate Cu 2 CO 3 (OH) 3 azurite, the blue, hydrated copper carbonate Cu 3 (CO 3) 2 (OH) 2 In these compounds, copper atoms from the metal surface have been fully oxidized into Cu+2 (cupric) ions. read more
The patina actually protects the copper below the surface from further corrosion, making it a good water-proofing material for roofs (which is why the roofs of so many old buildings are bright green). read more