Aron is a Rock/Steel type Pokemon. It evolves at Level 32 to Lairon and Level 42 to Aggron. Aggron's mega stone can be purchased at the Stone Shop in Anthian City for 200,000 Pokedollars.
Location: Gistening Grotto (at the route before Brimber City. In order to get there, you need Rock Smash.) It is somewhere in a small corner so look carefully!
Spawn Chance: Rare
If you have rock smash you only need to beat the 5th gym to use it outside battle and you need to teach
rock smash to a pokemon you own and make sure its on your team click on the boulderbehind some grasses on your way to brimber city