Weird geology

Not far from where General Washington made his famous crossing of the Delaware lies a strange place. Within a forest sits an open field, strewn with boulders and rocks of various shapes and sizes. The area seems devoid of any vegetation, save the lichens growing on the rocks. While such an area within the confines of Pennsylvania's forested Bucks County seems unusual in and of itself, it is a property of the rocks themselves that make the location so strange. They ring. Check out the story here. Your comment?