Question: where to get heracross mega stone in pokemon y?
Answer: The Heracronite is exclusive to Pokémon Y only. You can find the Heracronite in Santalune Forest in a patch of grass in front of the initial entrance to the forest (post-game.) For more help finding the Heracronite click on this video here. Note: It must be between 8pm and 9pm in the game for the stone to appear.