By Lea Shell
Middle school students are presented with a bucket of what, at first glance, looks like dirt. They pull handfuls onto their lab bench and carefully begin to sift.
“I found a shark tooth!” one student exclaims, prompting the rest of the class to peer more intently at their own piles. Before long, they see that the 10-million-year-old sediment that they’re sifting through—rejected from a nearby phosphate mine in North Carolina—contains the fossil remains of sharks. Some student