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An agitation leaching method was used for gold extraction from Aghdareh mine samples. Mineralogical study showed that 58% of the gold particles were finer than 10 µm. In addition 3% of the grade in the sample was related to refractory gold. Experiments results showed that at the optimum condition gold recovery was 91.8% and silver, and mercury recoveries were 41.5%, and 10.2%, respectively. After performing cyanidation tests for 6 different fractions, it was concluded that the most unleached gold particles exist in the fraction size finer than 25 µm and about 5% of gold particles in the fraction size larger than 25 µm was not leached. Therefore, further comminution was applied which increased by about 3.57% of gold recovery and about 5% of silver recovery. Further comminution did not affect the recovery of mercury. In order to increase the mercury recovery and prevent from amalgamation of gold by mercury particles, Knelson gravity concentrator was used. The tailing of gravity method was examined using cyanidation tests by considering the optimum conditions. According to the final results, using the combination of these methods, gold recovery is increased to 93.3% and the recovery of mercury increased to 42.1% while the recovery of silver is 42.17%, without noticeable change.

In this research work, agitation leaching of malachite using sulphuric acid solution was investigated in mechanical agitation reactor taking particle size, sulphuric acid stoichiometric ratio, solid percent and temperature as effective parameters. Based on results, malachite and azurite were found to be the main minerals of the representative sample. Sulphuric acid concentration effect in three different amounts of 5%, 10% and 20% was examined. To find out maximum sulphuric acid consumption vs. particle size, bottle roll tests were conducted. Full factorial design (24) with three centre points was applied to determine optimum conditions for three studied responses including copper recovery, iron recovery and sulphuric acid recovery. The optimum leaching conditions were found to be as follows: particle size, 600 microns: sulphuric acid stoichiometric ratio, 4: solid percent, 45%: temperature, 25°C. Under these optimum conditions, copper recovery, iron recovery and sulphuric acid recovery were 83.84%, 99.64% and 2.96%, respectively.