Cerium

Cerium is the most common of the rare-earth metals, about as abundant in Earth's crust as copper. Jöns Jacob Berzelius and Wilhelm Hisinger discovered it in 1803 and named it after Ceres, a dwarf planet found two years earlier. Like other rare earths, it is mined mostly in China.

In the television, cerium atoms scattered through the YAG phosphor are what glow. They absorb blue light from each LED chip and give off yellow, which blends with the remaining blue to look white. Cerium oxide is also the standard powder for polishing glass, including display glass, and scraping a cerium-iron alloy makes the sparks in lighters.