Clay dog

Clay dogs are naturally occurring clay formations that are sculpted by river currents from glacially deposited blue-gray clay and then dried by the sun. They exhibit tremendous variety in shape and size, with some being simple and others having highly complex forms. They only occur in a few places in the world; until recently, Croton Point along the Hudson River produced them, but the clay slope that produced the dogs was subsequently demolished to extend a park lawn. Clay dogs were described in detail in an article by L. P. Gratacap, Opinions on Clay Stones and Concretions.