Sterling silver necklace with 3 tourmalines. Cast directly from the casings of Caltrops--the strange and beautiful shell of a chestnut that grows in water. Native to Asia and Africa, the Caltrop shell is thought to bring good luck. In China it is regarded as an auspicious symbol of a bat, a very lucky animal. These Caltrop shells were found along the Hudson riverbed in Upstate New York.