An alloy dubbed PWA 1484, which Pratt & Whitney developed in the early 1980s, consists (by weight) of nickel (59 percent), cobalt (10 percent), tantalum (9 percent), aluminum (6 percent), tungsten (6 percent), and a few other elements (10 percent). One of the others is rhenium (3 percent), which provides a significantly higher metal temperature capability. Gell notes that rhenium is a “by-product of a by-product,” derived from specific copper-molybdenum ores, and a very costly element in limited supply.