The Element Encyclopedia of Witchcraft: The Complete A-Z for the Entire Magical World - Judika Illes 2005
Hag stone is another name for a holed or holey stone. Hag stones are pebbles containing natural perforations. They are considered extremely magical powerful, bestowing protection and fertility and granting wishes. Hag stones cannot be created; boring a hole through a pebble is insufficient, they must be created by nature. Occultists consider hag stones valuable talismans. Usually they are strung on a cord and worn around the neck or hung on a wall or over a bed.