In the core series games
If held by an
Steelix, allows it to Mega Evolve into Mega Steelix if its Trainer has a Key Stone. Each Trainer can only Mega Evolve one Pokémon per battle.
Unaffected by item negating effects (such as
Embargo and Klutz). Item manipulating effects (such as Trick and Fling) cannot give Steelix a Steelixite or remove a Steelixite from Steelix.
Outside of battle
If held by an Steelix, allows it to Mega Evolve into Mega Steelix when it performs a
Spectacular Talent during a Pokémon Contest Spectacular while its Trainer has a Key Stone. Steelix will remain a Mega Steelix until the Talent Round ends.
Pokémon holding Steelixite in
Pokémon Omega Ruby and Alpha Sapphire cannot be traded to Pokémon X and Y.
S M US UM One of a variety of mysterious Mega Stones. Have Steelix hold it, and this stone will enable it to Mega Evolve during battle.
Acquisition In the anime
A Steelixite in the
A Steelixite worn by
Brock's Steelix appeared in , where When Regions Collide! Brock used it to Mega Evolve Steelix during his battle with Kiawe. The Steelixite didn't appear equipped on Steelix, but rather, it appeared on its head right before Mega Evolving.
In other languages
大鋼蛇進化石 Dàgāngshé Jìnhuà Shí
大鋼蛇進化石 / 大钢蛇进化石 Daaihgongsèh Jeunfa Sehk