| abstract |
Copper porphyry ores, especially those too deeply buried for conventional open pit mining, are mined in place by an in situ leaching technique using as a leaching medium a mixture of dilute sulfuric acid, oxygen and nitrate ion added either as nitric acid or as an alkali metal or ammonium nitrate salt. The nitrate ion speeds dissolution of copper minerals, especially chalcopyrite, and the alkali metal or ammonium ion reacts with iron and sulfate in the leaching medium to deposit iron in the form of crystalline jarosites. Precipitation of iron within the ore body as a jarosite maintains the permeability of the ore body to the leaching medium thus increasing both the rate and the total recovery of copper as well as depleting the leach solution of unwanted iron. |