The price of rhenium (Re) hit $10,550 per kg recently, continuing a dramatic rise from the $1,330 average price in 2007 reported by the USGS. Two of the five mines that produce rhenium in the U.S. are in Arizona, one being Freeport's Sierrita mine near Green Valley, the other Asarco's Mission mine near Sahuarita.
Rhenium is used in gas turbine jet engines and as catalyst in petroleum refining. The U.S. last year imported 86% of its rhenium. Rhenium is a by-product of molybdenum production which in turn is a product of copper production from porphyry systems.
It is estimated that the Sierrita mine produces 4 tpy or 12.5% of the world's rhenium supply.
[right: Sierrita mine, infomine.com]