**3.2 Dump leaching**

Dump (run of mine) [18] leaching involves uncrushed waste rock and low grade ore is piled up or changing a pit to dump by blasting it. Conventional methods would be very expensive to process these type of ores samples, except dump leaching, dump can be very huge, containing in excess of 10 million tons of waste rock, up to 60 m deep [7, 30].

In order to digest some of unwanted minerals like silicate and to promote the growth of acidophilic microorganism, acid water solution is spread on the top surface, the acid water solution percolate through the dump, the more acidic the environment the more growth of microorganisms that oxidize minerals to be recovered. The pregnant leach liquor or acid run-off is collected at the bottom of the dump, from where it is pumped to a recovery station. After collection the process followed by solvent extraction, electro wining for the metal production but dump aeration is vital for the microorganism to growth, tailing from solvent extraction recycled on the top of dump. Escondida mine found Chile is the biggest bio dump leach in world [26, 30].
