Estimated Value (Sane Cost Guide): 1,000 gp
DMG Value: 501 gp - 5,000 gp
When you use an action to toss the clear spindle Sustenance Ioun Stone into the air, the stone orbits your head at a distance of 1d3 feet and you don't need to eat or drink while this clear spindle orbits your head. Thereafter, another creature must use an action to grasp or net the stone to separate it from you, either by making a successful attack roll against AC 24 or a successful DC 24 Dexterity (Acrobatics) check. You can use an action to seize and stow the stone, ending its effect.
A stone has AC 24, 10 hit points, and resistance to all damage. It is considered to be an object that is being worn while it orbits your head.
Source: DMG p176