Not all meteorites are created equal. The most common sort are chondrites. Chondrites are stony meteorites which compose approximately 80 percent of all meteorites. Achondrites, on the other hand, are much more rare; only 4-8 percent of all meteorites are of this type. They are so named because they contain no chondrules, which are round grains that give chondrites their distinctive character.
Members of the ureilite class of achondrite meteorites contain all sorts of cool stuff – olivine, pyroxenes, and sometimes even tiny diamonds can be found interspersed in their makeup. This makes for some intense microscopy, as shown above.