Aggronite is an item in the “Mega Stones” category (Items).
In-game descriptions
| X / Y | One variety of the mysterious Mega Stones. Have Aggron hold it, and this stone will enable it to Mega Evolve during battle. |
|---|---|
| Sun / Moon · Ultra Sun / Ultra Moon · Let’s Go, Pikachu! / Let’s Go, Eevee! · Sword / Shield | One of a variety of mysterious Mega Stones. Have Aggron hold it, and this stone will enable it to Mega Evolve during battle. |
Where to find it
Not placed on the atlas maps (so far: Red/Blue and Generation 3).
Sources : PokeAPI (items, item_flavor_text, machines) · atlas · pokeemerald species_info.h