If brought to the one of the following locations, the Helix Fossil can be regenerated into an Omanyte.
Generation I and III
In the Generation I and III games, the Helix Fossil is a Key Item.
In Pokémon Emerald, the Helix Fossil (as well as the Dome Fossil and Old Amber) is found in the game data, but it is not legitimately obtainable and has no effect. The player is unable to regenerate this fossil in the Devon Corporation.
Generation IV onward
From Generation IV onward, the Helix Fossil is no longer a Key Item, and is a normal item. Therefore, multiples of them can be obtained, they can be held, and sent to other players via trading.
||A fossil of a Pokémon that lived in prehistoric times.
||A piece of ancient marine Pokémon's seashell.
||A fossil of an ancient, seafloor-dwelling Pokémon. It appears to be part of a seashell.
|A fossil of an ancient Pokémon that lived in the sea. It appears to be part of a seashell.
|A fossil from a prehistoric Pokémon that once lived in the sea. It might be a piece of a seashell.