Last night on Mad Money, Jim Cramer outlined his Four Horsemen of Mining, including Companhia Vale do Rio Doce (RIO), BHP Billiton (BHP), Rio Tinto (RTP), and new favorite Teck Cominco (TCK). Cramer has called Companhia Vale do Rio Doce (RIO) or just "Rio" for short, a favorite of his, undervalued, and has twice cited monopoly power as a reason to own this mining conglomerate. His call to double down in February 2006 worked well until the market plunged in April 2006. Investors didn't see previous highs again until 2007. Cramer has been consistently positive on the stock except for a don't buy call in the September 13, 2006 "Sudden Death" when he suggested America Movil (AMX) over RIO because of its higher growth.