Rich copper deposits have been exploited in the orefield and are the result of supergene enrichment. Supergene enrichment is the result of changes in the water table and pH (hydrogen ion content) and Eh (electropotential). The process requires that the lode is porous so that surface oxygenated waters can descend and that it contains pyrite. The porosity of the lodes in the Cornubian orefield is due to the generally open texture, plus the extended period of weathering, particulary in the Tertiary Period. Lodes in the Cornubian Orefield often contain abundant pyrite, especially the upper parts. Pyrite, when oxidised by surface water, produces a weak sulphuric acid solution that can both attack other sulphides such as chalcopyrite, arsenopyrite, galena and sphalerite and the other soluble constituents of the lode, taking them into solution. Only resistate minerals like quartz and cassiterite remain with iron oxides and occasionally gold. This is known as gossan; and in the Cornubian orefield was enriched in tin due to the loss of sulphides due to oxidation. Below the water table the dissolved metals are precipitated. This process can therefore dissolve small percentages of metals in the upper part from large volumes of rock and redeposit them at a higher grade in a small volume of rock, especially in the case of copper. Immediately below the gossan is the oxidized zone containing malachite, azurite, cuprite and copper arsenates; below at the water table is the zone of supergene enrichment with native copper at the interface and chalcocite with bornite below; beneath this is the unoxidized ore, or proto-ore, of sulphides of pyrite, chacopyrite, arsenopyrite etc. Changes in the water table would redissolve and redeposit the metals producing a more complex mineral assemblage. An example of this is galena after pyromorphite, which illustrates that the process can be reversed with reducing conditions after oxidation.

An increase in the concentration of any of the elements in solution, change in pressure or temperature, reaction with the chemistry of the wall rocks and mixing with other solutions can initiate precipitation. The chemical reaction taking place is complex and is still poorly understood. The dissolution of the sulphides produces open spaces in which the aqueous metal bearing solutions can occupy to crystallize out forming beautifully formed minerals, especially in the oxide zone.