Mega Stone

are evolutionary stones that allow certain Pokémon to reach their final form for one-evolution families and second/true final form for two-evolution/branch-evolution families.

Each Mega Stone has a "-ite" or "-nite" on the end of it preceded by the related Pokemon's name.

Example:

Lucario's Mega Stone is called Lucario-"nite"

Blaziken's Mega Stone is Blaziken-"ite"

It is very possible that certain Mega stones like the Blazikenite can't be obtained through normal gameplay and only by means of special offers.

Certain Pokémon will be able to evolve into a Mega form with the use of a Mega Stone, a held object. However this evolution will devolve into to their pre-evolved form at the end of the battle.