"folk thunderstones", distinguishing his view from the popular one. His view was based on what may be the first in-depth lithic analysis of the objects in his collection, which led him to believe that they are artifacts and to suggest that the historical evolution of these artefacts followed a scheme.

Mercati, examining the surfaces of the ceraunia, noted that the stones were of flint and that they had been chipped all over by another stone to achieve by percussion their current forms. The protrusion