From publisher blurb:
In this supplement you'll find a baker's dozen (thirteen) of new ioun stones, those strange, gem-like creations that orbit their user which originated in the works of Jack Vance. The value and utility of the stones varies quite a bit. Each comes with an illustration as well as flawed and cracked versions.
An example of the ioun stones:
Bright Silver with Gold Flecks Pentacle: 3/day chance to fascinate 2d4+10 HD of creatures, as the spell hypnotic pattern