Hydrometallurgy currently accounts for approximately 21% of the world primary production of copper. Chile and the United States in 2010 produced 2.09 and 0.43 million mt, respectively, of high grade copper by leaching/solvent extraction/electrowinning methods. These numbers reflect a remarkable growth in copper hydrometallurgy over the past few decades. This growth can be directly attributed to a number of key innovations. Of these, copper solvent extraction certainly qualifies as a hallmark innovation. A review of these innovations shows that technology is quite fluid, that it diffuses and circulates between various mining and processing sectors. Furthermore, it normally requires a long incubation period for the complete acceptance and implementation of new technology.