Open Hole Core Clock approximately 4" in diameter from the Clear Fork formation located 4,900 feet below the surface. This rock is estimated at being 230 million years old. This Clock is a great display of the core sample formation and sets on your desktop or book shelve as a beautiful display of the oil formation below. Your Clock will be from the Clear Fork Formation. Each clock is unique, a one of a kind the clock. We wll deliver one from our stock that will be beautiful display the the creation of the Permian Basin. It is like a finger print of Earth's creation.