IIRC Aggronite is only found in Y while Tyranitarite is only found in X, but the complimenting pokemon are found in the opposite version. So X users can find aggron they just can't find the stone and the same goes true for Y users and Tyranitar. --- I've got a quote that embodies you perfectly, but it's seventy-three posts long, has a few massive flowcharts, and lots of Xion-KMA to Me
If you still haven't found it, you need to do a few things in post game until your mega ring gets upgraded. Then, from 8pm-9pm, the stone appears in Cyllage Gym --- --- Do I regret buying a replica master sword? My inner link says "no, they're crazy, you have the triforce". I'm with link on this one.