A cliff near Gulu, Guizhou Province, China, is said to “lay” mysterious egg-shaped stones every thirty years. Part of Mount Gandeng, Chan Da Ya — Mandarin for “egg-producing cliff” — is 20 feet high and 65 feet wide. It has an uneven surface, and every three decades, erosion causes each hollow to emit an oval-shaped, perfectly smooth rock, which eventually falls to the ground, like a hen laying an egg. These are collected by villagers who believe the stones bring good luck. (from Ripley’s Believe It Or Not: Beyond the Bizarre)
Sylvia Shults, author 