A crystal ball is a crystal or glass ball believed by some people to aid clairvoyance. It is sometimes known as a shew stone. A body of water, either in a container or on the ground, used for this purpose, is called a scrying pool.
Celtic tribes, known to exist in Britain as early as 2,000 BC, were unified by a priesthood known as Druids. Druids are one of the earliest known peoples to have used crystals in divination. It is interesting to note that Druid religion had similarities to megalithic religion of an “earlier” Britain, thus it is possible the first use of crystal divination might have come from them.
Later, during central Europe’s Medieval Period (AD 500–1500), seers, wizards, sorcerers, psychics, gypsies, fortune tellers, and all other types of diviners also used crystals to “see” into the past, present, or future.
Due to its transparent nature, a natural gemstone called beryllium aluminum silicate (beryl) was often used for divination. Scottish Highlanders termed these objects “stones of power.” Though early crystal balls were made from beryl, they were later replaced by rock crystal, an even more transparent rock.