A crystal ball, also known as an orbuculum, is a crystal or glass ball and common fortune telling object. It is generally associated with the performance of clairvoyance and scrying in particular. Crystal balls are common in stage magic acts.
In numerous fantasy works of Harry Turtledove, crystal balls (often called crystals) serve as analogs of the telegraph, the telephone, radio, film, television, and/or the Internet, depending on the level of development in a story's civilization. The analogy is not always clear cut. For example, the crystals in The War Between the Provinces are much more efficient than the telegraph that was available during the American Civil War.