Why ringing rocks sing

Transcript

In the wild, these are called ringing, sonorous, or lithophonic rocks, because they give off a clear bell-like tone when hit with metal. The best-supported explanations point to dense, fine-grained igneous rock, such as diabase, where sound waves travel efficiently and the pitch depends on the stone's size and shape. In places like Montana and Pennsylvania, scientists also suspect internal stress and the way the boulders are stacked or suspended help the stones ring, while only some rocks in a field make the sound.