Fairy Loaves

Myths, folklore, and symbolism
Fairy Loaves: A name for fossil sea-urchins, because their plump domed shape, with five lines at the apex, resembles a small round loaf. They are found in chalky downland; they were said to be lucky, and whoever finds one should spit on it and toss it over his left shoulder. In Suffolk, where they were usually polished with black led, it was said people who kept one in the house would never lack bread. They were also called shepherd's crowns, and were sometimes used as thunderstones. (Oxford Dictionary of English Folklore)

Do you know of fairy loaf folklore from other countries?