There are basically four kinds that are used a lot. One is the solid glass gazing ball, which is cheap. As long as there are no bubbles and the distortion is manageable, these are fine. The second kind is made of glass and so-called "lead" crystal. As long as they are free of bubbles, distortion, and dark tint, these are acceptable. Reconstituted quartz crystal balls are the third type. These are the best option for most people because they are inexpensive and still made of pure quartz. The term "reconstituted" refers to pure quartz that has been ground, heated, and then shaped into a sphere. Pure quartz spheres are the fourth type. These are significantly more costly and never entirely clear. They have beautiful inclusions that give it the "ice" look that the Greeks said it had. Because they are pure quartz in its natural state, some people enjoy gazing at them. Others would rather have a crystal-clear sphere rather than the inclusions for stargazing.