Copper-containing rock, or copper ore, holds only a small percentage of copper. Most of the rock is unwanted material, typically referred to as gangue.
There are two main copper ore types of interest: copper oxide ores and copper sulfide ores. Both ore types can be economically mined, though they are processed in different ways. Copper sulfide ores are typically the most profitable copper ores to mine. That is because they have high copper content, and the copper in them can more easily be separated from unwanted minerals. However, copper oxide ores are more abundant.
Read on for an overview of copper oxide ores and copper sulfide ores, with a focus on how they’re processed. For investors interested in the copper space, having a good handle on this information can be an important part of deciding which companies are the best to invest in.
Copper ore types: Oxides
As mentioned, copper oxide ores are not as attractive an exploration target as copper sulfide ores due to their lower grade. However, in some cases low-grade copper oxide ores can still be economically mined because they can be processed at a lower cost than copper sulfide ores.
Oxidized copper orebodies may be treated in several ways. For instance, hydrometallurgical processes are used to treat copper oxide ores that are dominated by soluble minerals, such as copper carbonate minerals. These copper oxide ores are usually leached using sulfuric acid to liberate the copper minerals into a solution of sulfuric acid laden with copper sulfate solution.
The copper sulfate solution (called the pregnant leach solution) is then stripped of copper via a solvent extraction and electrowinning (SX-EW) process. Alternatively, the copper can be precipitated out of the pregnant leach solution through a process called cementation, whereby the copper is contacted with scrap iron. Copper produced through cementation is usually less pure than SX-EW copper.
Copper ore types: Sulfides
Different methods are used to process copper sulfide ores depending on the concentration of copper within the ore — higher-concentrated ores can be separated via smelting, while lower-concentrated ores are separated via hydrometallurgical processes.
Some supergene sulfide deposits can be leached using a bacterial oxidation heap leach process to oxidize the sulfides to sulfuric acid. That also allows for simultaneous leaching with sulfuric acid to produce a copper sulfate solution. As with oxide ores, SX-EW technologies are used to recover copper from a pregnant leach solution. Secondary sulfides, which are formed by supergene secondary enrichment, are resistant to sulfuric leaching.
When rich enough, native copper orebodies may be treated to recover contained copper via a gravity separation circuit. Supergene copper ores rich in sulfides may be concentrated using froth flotation.
Copper ore types: More information
The above information provides a good overview of copper ore types and how they’re processed, but as all savvy investors know, more information is better. We suggest reading our article on world-class copper deposits to get a better understanding of how copper is found and how miners extract it.
This is an updated version of an article first published by the Investing News Network in 2011.
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Securities Disclosure: I, Amanda Kay, hold no direct investment interest in any company mentioned in this article.