Pokémon X & Y Cheats: How to obtain Manecite and Houndoomite to get Mega Manectric and Mega Houndoom
Mega stones! You want 'em! We know where to find 'em!
First, keep in mind that you won't be able to find these Mega Stones until you beat the game and complete a slew of quests to unlock this ability. You can find the tutorial on how to start hunting for Mega Stones here.
Also one of the easier Mega Stones to find. You'll want to start off by using Fly into Dendemille Town. From there, head West through the exit which will bring you to Route 15. Immediately after coming out in Route 15, head South. You'll need to use Strength to push a block into the ground to clear the way.
Just follow the path going South until you reach a rectangular rock formation with two skaters skating around it. The Mega Stone for your version's respective Pokemon will be in the South part of that rock.
As always, remember to do this after 8PM and before 9PM and after touching the Sundial in Anistar City.