This lasts for 10 minutes, but can be canceled at any time by right-clicking the icon (), by selecting the icon and canceling it in the equipment menu (), by double-tapping the buff icon (), or by canceling the buff from the buffs screen (). The Clairvoyance buff can be refreshed limitlessly, with no cooldown period or restrictions on use.
The Crystal Ball is not equipable in an accessory slot, and must be placed instead in order to activate the buff. It can be mined with a pickaxe or drill and picked up again, even while the buff is active, which will not cancel the buff.
The Crystal Ball is the only crafting station which provides buffs, unlike the Sharpening Station, Ammo Box, and Bewitching Table, which provide the 10 minute buffs for the other 3 main classes (Melee, Ranged and Summon, respectively), allowing Pure Mages to save money by only needing to purchase the Crystal Ball rather than another class potentially needing their respective buff structure as well as the Crystal Ball.
This is particularly notable for Ranged users, who would benefit from the Endess Quiver or Musket Pouch, as the Ammo Box cannot be found naturally generated in the world; Sharpening Stations can be found in Underground Cabins and Bewitching Tables can be found in the Dungeon.