If held by an Alakazam (or is present in the player's BagPE), the Alakazite allows it to Mega Evolve into Mega Alakazam if its Trainer has a Key Stone. A Trainer can only Mega Evolve one Pokémon per battle (or only have one Mega-Evolved Pokémon at any given momentZA).
As a Mega Stone, it is unaffected by item-negating effects (such as Embargo and Klutz). Item-manipulating effects (such as Trick and Fling) cannot give or remove an Alakazite from Alakazam.
Outside of battle
If held by an Alakazam, the Alakazite allows it to Mega Evolve into Mega Alakazam when it performs a Spectacular Talent during a Pokémon Contest Spectacular if its Trainer has a Key Stone. Alakazam will remain a Mega Alakazam until the Talent Round ends.
An Alakazite belonging to a Trainer appeared in Mega Evolution Special IV, during the ten-battle gauntlet Lysandre had arranged for Alain's training. The Alakazite was attached to the Alakazam's right spoon.
Merchandise
The Alakazite has been featured in several officially licensed merchandise.