In the core series games
If held by a 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 a 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.
| One of a variety of mysterious Mega Stones. Have Steelix hold it, and this stone will enable it to Mega Evolve during battle.
In spin-off games
|| This section is incomplete.|
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In Pokémon Shuffle, the Steelixite allows the player to Mega Evolve Steelix.
The player can obtain the Steelixite by completing the competitive stage available in Week 23 of the event rotation.
The Steelixite was also available as a prize during the Mega Steelix Competitive Stage. This Competitive Stage ran on the Nintendo 3DS version from December 1 to 8, 2015; August 2 to 9, 2016 and September 26 to October 3, 2017. It ran on the Pokémon Shuffle Mobile from August 2 to 9, 2016; and September 26 to October 3, 2017.
The Steelixite enables the following Mega Evolution:
|| Mega Steelix
|| Erases unbreakable-block disruptions (max 10) and damages the foe.
Does +100 damage per block erased.
In the anime
In other languages
|| 大鋼蛇進化石 Daaihgongsèh Jeunfa Sehk
|| 大鋼蛇進化石 / 大钢蛇进化石 Dàgāngshé Jìnhuà Shí
|| 강철톤나이트 Gangcheoltonnite