Question

Where are Thunder Stones in X & Y?

Answer 1

Non-repeatable

• Route 10 (In the northwest corner of the middle rock-bordered field of large menhirs)
• Route 11 (On the small crystal pillar at the easternmost end of the route [*hidden*])

Repeatable

• Secret Super Training (Follow Those Fleeing Goals!, The Battle for the Best: Version X/Y!)
• Route 18 (From Psychic Inver for defeating him)
• Spiky Rock 2 (Hitting this background object with Hyper Voice or Rock Slide on Routes 8, 9, 13 18, 19)

Answer 2

You can go to the Stone Emporium in Lumiose city.At first there will only be the fire,water and leaf stones which cost 1200 poke dollars.After progressing in the game come back to the emporium and the Thunderstone will be there.

Answer 3

Adam's answer is correct, but you can also find it through super training as one of the secret training prizes.