The rare earths aren't really all that rare. While they're widely distributed all over the earth they're rare enough in the sense that there aren't that many locations where you can find them in concentrated deposits that make mining profitable. And when you do find those deposits the refining steps yield misch metal which is sort of an onomatopoeia for what it actually is: a mishmash of seventeen different metals. Getting those isolated from each other has been rated as one of the major chemical engineering headaches of metallurgical science! In any case, cerium will account for about half of the misch metal alloy and is the most abundant of those 17 elements.
Our cerium sample comes in a little argon-filled ampule to protect it from oxidation and weighs approximately one gram.