Heap leaching
Heap leaching is an industrial mining process used to extract precious metals, copper, uranium, and other compounds from ore using a series of chemical reactions that absorb specific minerals and re-separate them after their division from other earth materials.
Through procedures that go beyond the commonly employed metallurgical testing and the integration of data gleaned through real time 3D monitoring, a more complete representative characterization of the physicochemical properties of the heap environment is obtained.
This improved understanding results in a significantly higher degree of accuracy in terms of creating a truly representative sample of the environment within the heap.
[citation needed] The production of one gold ring through this method, can generate 20 tons of waste material.
[8] The largest copper heap leach operations are in Chile, Peru, and the southwestern United States.
Higher-grade ores are usually put through more complex milling processes where higher recoveries justify the extra cost.
The method was originally patented by Australian miner BHP and is being commercialized by Cerro Matoso in Colombia, a wholly owned subsidiary of BHP; Vale in Brazil; and European Nickel for the rock laterite deposits of Turkey, Talvivaara mine in Finland, the Balkans, and the Philippines.
Nickel recovery from the leach solutions is much more complex than for copper and requires various stages of iron and magnesium removal, and the process produces both leached ore residue ("ripios") and chemical precipitates from the recovery plant (principally iron oxide residues, magnesium sulfate and calcium sulfate) in roughly equal proportions.
While most mining companies have shifted from a previously accepted sprinkler method to the percolation of slowly dripping choice chemicals including cyanide or sulfuric acid closer to the actual ore bed,[9] heap leach pads have not changed too much throughout the years.
The conventional pads simplest in design are used for mostly flat or gentle areas and hold thinner layers of crushed ore.
Many of these mines which previously had digging depths of about 15 meters are digging deeper than ever before to mine materials, approximately 50 meters, sometimes more, which means that, in order to accommodate all of the ground being displaced, pads will have to hold higher weights from more crushed ore being contained in a smaller area (Lupo 2010).
With the rise of the environmentalist movement has also come an increased appreciation for social justice, and mining has showed similar trends lately.
Societies located near potential mining sites are at increased risk to be subjected to injustices as their environment is affected by the changes made to mined lands—either public or private—that could eventually lead to problems in social structure, identity, and physical health (Franks 2009).
have argued that by cycling mine power through local citizens, this disagreement can be alleviated, since both interest groups would have shared and equal voice and understanding in future goals.
If communities are able to feel like they have a valid understanding and power in issues concerning their local environment and society, they are more likely to tolerate and encourage the positive benefits that come with mining, as well as more effectively promote alternative methods to heap leach mining using their intimate knowledge of the local geography (Franks 2009).
