Some Members of Congress have expressed concern over U.S. acquisition of rare earth elements that are used in various components of defense weapon systems. Rare earths are a collection of 17 elements on the periodic table, including a series of 15 elements beginning with atomic number 57 (lanthanum) and extending through number 71 (lutetium), as well as two other elements, yttrium and scandium, which have similar properties. These elements are referred to as "rare" because while they are relatively abundant in total quantity, they appear in low concentrations in the earth's crust and economic extraction and processing is both difficult and costly. From the 1960s to the 1980s, the United States was the leader in global production of rare earths. Since that time, production of the world's supply of rare earths has shifted almost entirely to China, in part due to lower labor costs and lower environmental standards. China produces about 97% of rare earth oxides, is the only exporter of commercial quantities of rare earth refined metals, and is the majority producer of the world's two strongest magnets (samarium cobalt (SmCo) and neodymium iron boron (NeFeB) permanent rare earth magnets). However, Molycorp, a U.S. company with mining operations in ...