Hard Stone is an item in the “Type enhancement” category (Items). It costs ₽1000.
In-game descriptions
| Ruby / Sapphire · Emerald | A hold item that raises the power of ROCK-type moves. |
|---|---|
| FireRed / LeafGreen | An item to be held by a POKéMON. An unbreakable stone that boosts the power of ROCK-type moves. |
| Diamond / Pearl · Platinum · HeartGold / SoulSilver · Black / White · Black 2 / White 2 | An item to be held by a Pokémon. It is an unbreakable stone that ups the power of Rock-type moves. |
| X / Y | An item to be held by a Pokémon. It is a durable stone that boosts the power of Rock-type moves. |
| Sun / Moon · Ultra Sun / Ultra Moon · Let’s Go, Pikachu! / Let’s Go, Eevee! · Sword / Shield | An item to be held by a Pokémon. It’s a durable stone that boosts the power of Rock-type moves. |
Where to find it
Not placed on the atlas maps (so far: Red/Blue and Generation 3).
Held by wild Pokémon (Generation 3)
Common: 50% · rare: 5% (60% / 20% with Compound Eyes in the lead), from SetWildMonHeldItem.
| Rare |  Aron  Lairon  Aggron |
|---|
Sources : PokeAPI (items, item_flavor_text, machines) · atlas · pokeemerald species_info.h