Ringing Rocks

A field of gray diabase boulders in the Bucks County woods that ring like struck bells when you tap them with a hammer, a clear metallic bong instead of a dull thud. Only about a third of them ring, nobody nearby can say quite why, and a patch of dead ground sits at the center where little grows. The physics is real and the mystery is real enough to keep the hammers coming. Bring one and listen.