Mega Stones are held items introduced in Generation VI. They make a debut appearance in Pokémon X and Pokémon Y. They are used to Mega Evolve Pokémon into their Mega counterparts. Mega Stones are not actually called Mega Stones, but rather a specific item name. So far, it seems that the majority of Mega Stones will be the name of the Pokémon with "nite" added or dropping the "n" of a Pokémon's name to add it.
Below is a list of the currently revealed Mega Stones:
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