text: In the 16th century, heap leaching became commonly used to extract copper as well as saltpeter, from organic matter. Primarily used in Germany and Spain, pyrite would be brought to the surface and left out in the open. The pyrite would be set outside for months at a time, where rain and air exposure would lead to chemical weathering. A solution containing copper sulfide would be collected in a basin, then precipitated in a process called cementation, resulting in metallic copper. Heap leaching, in this natural chemical-free form, was further developed to obtain different, more economically viable, types of ore. This was done by incorporating chemical lixiviation, which applies more chemical manipulation and technique to heap leaching.
  From 1767-1867, the production of potash in Quebec became an important industry to supply France's glass and soap manufacturers. Potash was most frequently made from the ash remains of wood-burning stoves and fireplaces, which were agitated with water and filtered. Once evaporated, the remains would be potash. 400 tons of hardwood would be required to burn to yield one ton of potash. 
  In 1858, Adolf von Patera, an Austrian metallurgist, utilized lixiviation to separate soluble and insoluble compounds from silver in an aqueous solution.The technique of Patera's lixiviation was further developed by American E. H. Russell around 1884, creating the "Russell Process". In 1887, when the cyanidation process was patented in England, it began to be incorporated into the existing leaching process, creating the more specific cyanide leaching.
  In 1887, when the cyanidation process was patented in England, it began to phase out the existing Russell Process. Cyanidation was much more efficient and had a recovery rate of up to 90%.
  Leading up to World War I, many new ideas for leaching processes were experimented. This included using ammonia solutions for copper sulfides, and nitric acid for leaching sulfide ores. Most of these ideas were phased out into obscurity due to the high cost of the leaching agents required.