The Girilambone copper deposit of New South Wales, Australia, serves as an end-member model for development of a classic oxidation-zone profile in an environment virtually free of both the effects of active tectonics and significant fluctuation in the local water table. The oxidation zone of other copper deposits may be interpreted for history of recently active tectonics, palaeoclimate, and water-table stability by comparison to the Girilambone deposit. Unlike the oxidation profiles of porphyry copper deposits of western North America, which have been overprinted by many water-table fluctuations produced by active tectonics, the Girilambone deposit appears to have little modification to the original oxidation profile. Oxidation of primary sulfides at Girilambone was an exothermic process facilitated by chemolithotrophic bacteria, recorded by malachite oxygen isotope thermometry estimates of up to 52°C, and very light malachite carbon isotope values. The bacteria generated CO2 which migrated upwards to react with copper rich meteoric fluids of the vadose zone to precipitate malachite. Unlike porphyry copper deposits of western North America which experienced recent tectonic activity, the secondary minerals (clays, iron oxides and copper carbonates) at Girilambone were not repeatedly fractured and offset during oxidation to re-establish permeability. This reduced permeability of the oxidation zone and slowed the release of CO2 from the system, producing significantly elevated partial pressure of CO2, sufficient for azurite formation to dominate. Azurite oxygen and carbon isotope values indicate formation at lower temperatures up to 32°C, and with less bacterial activity than for malachite. The sulfide-digesting bacteria at Girilambone were relatively free of seasonal swings in population, as the deposit does not have the interbanded azurite and malachite typical of episodic bacterial populations triggered by seasonal precipitation. Thus the absence of significant Cu-carbonate banding at Girilambone serves as a palaeoclimate indicator. Deeper in the Girilambone oxidation zone, native copper and cuprite dominate, whereas chalcocite formed an enrichment blanket just above and at the modern water table. Oxygen and carbon isotope values for pseudomorphs of malachite after azurite indicate that these were generated as a retrograde reaction when CO2 production from bacterial digestion of sulfides waned and temperatures in the oxidation zone were near ambient. In the post mining environment, chloride-rich groundwater seeps actively precipitate atacamite, while exposed remnants of sulfide masses form an outer rind of porous malachite. Exceptions to this oxidation zone sequence occur due to localised fluid channelisation and perched water-table lenses that generated mineralogical overprints.

A thorough assessment of the secondary minerals on 796 Chinese Pb-Cu-Sn-Zn bronze coins from ∼1100 BC to AD 1911 has been made. Malachite is found on more than 80% of the coins irrespective of their dynasties, but a botryoidal texture is only observed on the coins of the Song dynasty or older. Azurite, however, is seen in microscopic quantities on a single coin of ∼AD 1800, but is clearly visible on the Ming dynasty or older coins. Cerussite is a common secondary mineral of the Qin dynasty and older coins, though it has not been found on the Qing dynasty or younger coins. Cuprite is observed on the Song dynasty and older coins.

Stability relations of malachite and azurite are calculated and shown in Eh-pH diagrams, using ΔF (Gibbs free energy) values listed in Garrels and Christ (1965). The malachite/azurite transition is very sensitive to small chemical changes in the environment: equilibrium is reached at PCO2 = 10−3.45 atm., i.e. close to normal values, whereas the precipitation of both minerals from cupric-ion-bearing solutions takes place at pH values between 6 and 8, depending CO2 partial pressures. It is shown that stability relations of these minerals can be better explained in terms of activities of the carbonate and bicarbonate ion.

Azurite can be formed only under relatively acid conditions at relatively high carbonate activities. Since the latter imply mostly basic conditions, this explains why malachite is the more common form of copper carbonate and that azurite can be formed only under rather unusual conditions. It also explains the frequent alteration of azurite into malachite, due to small changes in carbonate/bicarbonate activities. These alterations include pseudomorphs of malachite after azurite.

The discoloring interaction between the artist's pigments cadmium yellow and the copper-containing malachite, an interaction that is conjectured to cause black spotting in oil paintings of the 19th and early 20th centuries, was examined using X-ray mapping and scatter diagram analysis. The application of these coupled techniques confirmed that copper sulfide phases were produced during discoloration reaction. Scatter diagram analysis indicated that two copper sulfide stoichiometries (CuS and Cu3S2) were present as reaction products where previously only crystalline CuS (covellite) had been identified by X-ray diffraction. The results demonstrate the potential of X-ray mapping coupled with scatter diagram analysis for the identification of both crystalline and X-ray amorphous phases produced by such complex heterogeneous interactions and their applicability to the investigation of interactions of artists' pigments.