Crystal Balls

Crystal balls are glass or quartz spheres used for the art of divination. Some seers and fortune tellers use them for scrying, while others use the featureless surface to clear their minds to open up to intuition. They are said to work best when the sun is at its northernmost declination. (Wikipedia 2015)

 Crystal balls are often used to communicate with the spirit realm, and in some cases crystals have also been used to contain invoked spirits.