Basic copper carbonate

Basic copper carbonate normally refers to the compound (Cu₂(OH)₂CO₃) (the mineral malachite). Sometimes the name is used for Cu₃(OH)₂(CO₃)₂ (the related mineral azurite). Malachite and azurite can be found in the verdigris patina that is found on weathered brass, bronze, and copper. The composition of the patina can vary, in a maritime environment depending on the environment a basic chloride may be present, in an urban environment basic sulfates may be present.