You find one in the ss libra.
you can get a fire stone in the ss libra in the deep part of the hull.
They can be sold at kecleon shops in dungeons
usually,in a dungeon if you find a kelcleon shop.Or you could trade from Pokemon ex of time/darkness.
win 2nd place at a bug catching competition (fire stone or thunder stone 1st place sun stone)
how should i no
A fire stone is used on certain Pokemon to make them evolve. The Pokemon that evolve with a fire stone are: ~Evee ~Vulpix ~Growlithe
Only once you can get this, in gateon port to the west is a shop inside a sailor is there he will notice your evee and will let you take a stone or item to evolve it take the fire stone then use it to evolve your evee to flareon.
Pansear uses a fire stone to evolve into Simisear.
Fire stone
EEVEE EVOLVES from FIRE STONE into FLAREON
A total of three Pokemon evolve using the Fire Stone: Vulpix, Eevee, and Growlithe.
Yes you can you get it in the beginning of the game at gateon port you have to talk to the shopkeeper in the shop which is on the left side of gateon port