Cerium

Cerium is a soft, silvery-white lanthanide metal that loses its shine as it reacts with air. Although classed as a rare-earth element, it is more abundant in Earth's crust than lead. It occurs combined with other elements in minerals, especially bastnäsite and monazite. These ores are processed chemically to separate cerium from the other rare earths, often recovering it as cerium dioxide. This compound is used to polish glass and in catalytic converters that help reduce harmful vehicle emissions. Cerium also helps make sparks: it is a major ingredient in ferrocerium, the metal alloy used in many lighter flints. Tiny particles of the alloy ignite when scraped away, producing the sparks that light the fuel.