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The Rockium Z (Japanese: イワZRock Z) is a type of Z-Crystal introduced in Pokémon Sun and Moon. It is the type-specific Z-Crystal associated with the Rock type and allows Pokémon to upgrade their Rock-type moves to Z-Moves.
Unaffected by item negating effects (such as Embargo and Klutz). Item manipulating effects (such as Trick and Fling) cannot remove a Z-Crystal from a Pokémon.
A full set of type-specific Z-Crystals, including the Rockium Z, appeared in A Grand Debut!, where Hapu allowed Ash to choose his grand trial prize from them.