Although pure iron sulfide does not contain copper, a relationship between iron sulfide and copper may develop under certain conditions. For example, in certain geological environments, iron sulfide minerals may coexist with copper-bearing minerals. During mining and refining, iron sulfide minerals may absorb or incorporate trace amounts of copper.
Furthermore, iron sulfide may interact with copper during certain chemical reactions or processes. For example, in metallurgy, iron sulfide can be used as a reducing agent to extract copper. This does not necessarily mean that the iron sulfide itself contains copper, but rather that it interacts with copper during the reaction.