Freeport-McMoRan Copper (FCX) has been a big on and off investment of Stone Fox Capital. They currently rank as the top independent producer and the 2nd overall behind Chile state owned Codelco. FCX has a big lead over BHP Billiton (BHP) as well.
This list further highlights the focus on FCX as a proxy for copper. Without doing a lot of research, the other public companies listed only have a small focus in copper. Number 9 Southern Copper (SCCO) is the only other option that is at least investable on US exchanges. SCCO has a $30B market cap so it isn't that small considering the big difference in production as compared to FCX.
1. Codelco 1,757 2. Freeport-McMoRan Copper & Gold Inc. 1,441 3. BHP Billiton Ltd. 1,135 4. Xstrata Plc 907 5. Rio Tinto Group 701 6. Anglo American Plc 645 7. Grupo Mexico 598 8. Glencore International AG 542 9. Southern Copper Corp. 487 10. KGHM Polska Miedz SA 426
* according to London-based metals-consulting company CRU. Production numbers are in thousands of metric tons.