More On Rare Earth Metals

Discover Magazine:

But the commercial versatility of the lanthanides extends far beyond the world of electronics. Cerium is a prime example. It was discovered in 1803 by Swedish chemist Jöns Jacob Berzelius, who named it after the asteroid Ceres, discovered two years earlier. (Ceres was then regarded as a new planet and so was much celebrated.) In 1885 the Viennese chemist Carl Auer von Welsbach found that a pinch of cerium oxide, together with thorium oxide, usefully increases the brightness of a gas lamp. Soon after, Auer discovered that a mixture of cerium and iron readily generates sparks. The alloy, which he modestly called Auermetall, is still used to ignite the flame in cigarette lighters.
Cerium’s applications kept multiplying. A fine powder of cerium oxide, known as optician’s rouge, is an excellent abrasive for polishing glass. Cerium compounds form nontoxic red pigments that are used in toys and household products. In medicine, cerium compounds were once administered for everything from tubercular coughing to seasickness; today those treatments are mostly regarded as quackery, but the element still earns its place in hospitals as an antiseptic wash for severe burns.
You may have cerium oxide in your kitchen if your oven is a self-cleaning model; it helps breaks down burned-on leftovers. You certainly have cerium oxide in your car, assuming it is less than 35 years old. The compound works to convert carbon monoxide emissions in automotive exhaust to less harmful carbon dioxide. As a fine powder mixed into diesel fuel, cerium oxide can also clean up the sooty fumes produced by trucks and buses. Industry consumes 55,000 tons of cerium every year. The element, pulled from a type of weathered granite called monazite, fetches about $60 a pound.

The article also mentions that scandium is used in aluminum softball and baseball bats, to prevent cracking.