Pokemon such as eevee, growlithe, and vulpix.
there is a firestone in fiery pass
With a Firestone you can evolve into a Eevee into a Flareon, A Vulpix into a Ninetails and a Growlithe into a Artacaine
firestones are for Pokemon who only are fire types
Pokemon Ruby has Pokemon that Pokemon Sapphire does not and Pokemon Sapphire has Pokemon that Pokemon Ruby does not.
It is used for the move tutor, who teaches you Pokemon old moves that they have forgotten.
there is a firestone in fiery pass
just give the right stone to it and it will evolve straight away e.g. eevee+firestone =flareon
an eevee
Vulpix.
Bring a Pokemon that knows strength to the Fiery Path (located between the sandstorm/desert and Lavaridge Town. Navigate the maze of boulders and at the end you will find a Pokeball that contains a Firestone.
With a Firestone you can evolve into a Eevee into a Flareon, A Vulpix into a Ninetails and a Growlithe into a Artacaine
Pokemon ruby's version IS Pokemon ruby.
I don't think it's obtainable in Ruby.
firestones are for Pokemon who only are fire types
Flameon is one of them
Pokemon Ruby has Pokemon that Pokemon Sapphire does not and Pokemon Sapphire has Pokemon that Pokemon Ruby does not.
you can find a firestone in national park after you get enough points you can buy one