Evolving Onix into Steelix requires a special item : r/pokemongo

Onix (Pokémon) - Bulbapedia, the community-driven Pokémon encyclopedia, onix pokémon go

Pokémon GO: Mega Steelix Energy Timed Research Tasks and Rewards

Idea to add Crystal Onix from the anime in special research : r/pokemongo, onix pokemon go

Pokemon Go - NEW Evolves! Start saving candy MEGA ONIX and 5 other EPIC evolves , onix pokemon evolution

Idea to add Crystal Onix from the anime in special research : r/pokemongo, onix pokemon go

How can players obtain rare Pokémon and special items (like evolution stones) in Pokémon GO? - Quora

Pokémon Legends Arceus special evolution requirements guide - Polygon

Soilix Onix Pre Evolution by Hyperagua on DeviantArt, onix pokemon evolution

Trading - Pokemon Gold, Silver and Crystal Guide - IGN