Cerium is the most abundant of the rare earth metals (not that, as we've already discussed, any of them are all that rare). It is also the most easily separated of the bunch thanks to an unusual oxidation state that is unique in this series. Still, not that rare does not make cerium exactly "common" in the sense that there's anything around your house made of it. Actually, that may not be true. There is one exception. If you look at the little wheel spinner on a cigarette lighter you'll notice a little black stick poking out against it. That's misch metal, an alloy that is at least 50% cerium with the remainder being the least valuable members of the rare earth group (mostly lanthanum and praseodymium). And so it is that cerium, which throws a furious amount of sparks when rubbed, became the world's favorite fire starter.

Cerium is a delicate metal that tarnishes when exposed to air which is why we'll ships yours with a light coating of oil. Even in oil the surface will turn dark as the cerium reacts chemically with even the smallest traces of impurities making it appear as thought the metal itself is menacingly dark. Luckily, it's pretty harmless. Another interesting tidbit: cerium is one of the least sonorous metals. When struck with another metal or is dropped it makes a hollow clank. A bell made out of pure cerium would ring out as if it was made of clay!

As many other rare earths, cerium oxidizes easily in air so must be kept stored in mineral oil or under a noble gas to keep it from degrading.

Note additional options for this element on the Ampules section

CAS 7440-45-1