Turning to Stone Marcia Bjornerud Flatiron Books, $28.99 Marcia Bjornerud sits in the basement of a soon-to-be-demolished building at Lawrence University in Appleton, Wis.

John K. Murray However, not every type of rock has the characteristics needed to be flaked into a tool. You want the stone to exhibit what’s called conchoidal fracture.

Were Stone Age humans the first geologists? Humans living in what is now South Africa 70,000 years ago possessed a surprisingly sophisticated understanding of the various kinds of rock that made up ...