You might want to look at
http://www.azstrut.org for some information. There is no good information there about what is done with hardware which is no longer reusable and I have sent an email to Ken about that. In fact, they send stuff the program cannot use to West-Tech for proper recycling and West-Tech pays AZStRUT for it so even junk is useful to the program.
Yes, there are companies that mine metals, such as gold, from old electronic parts and I am sure West-Tech does that. It is what makes green recycling profitable. In this case, some of that pays a small part of the cost of operating AZStRUT. But I don't think that is the kind of mining you were referring to.