There are 14 sorts of useful ioun stones. 

These magical stones always float in the air and must be within 3-ft of their owner to be efficacious. 

The new possessor of the 'stones must hold each and then release it, so it takes up a circling orbit, whirling and trailing, circling at 1-ft to 3-ft radius of his or her head. Thereafter, they must be grasped or netted to separate them from their owner. 

The owner may voluntarily seize and stow the stones (at night, for example) to keep them safe. He or she would of course lose the benefits during that time. 

From 1-10 ion stones will be found. Dice for the property of each stone, a duplication indicating a stone which is burned out and useless:

* After absorbing 10-40 spell levels the stone burns out and turns to dull gray, forever useless.

** After absorbing 20-80 spell levels the stone burns out and turns dull gray, forever useless.

*** Adds 10 points to psionic strength total, 50 maximum points.

Whenever ion stones are exposed to attack, they are treated as armor class -4 and take 10 hit points of damage to destroy. 

They save as if they were of hard metal, +3.