I went in the Glittering Cave at night but its still not here why can't I find it? is this a glitch?
These two things need to be checked:
Make sure your 3DS time is between 8 and 9 pm
Make sure you have upgraded your Mega Ring, you can do so by defeating the Champion and then defeat your Rival in Kiloude City. He/She will tell you that Sycamore wants to talk to you in front of the giant Gemstone in Anistar City, there he will upgrade your Mega Ring.
If it works the Kangakhanite will sparkle when you get close
Look at my answer and you will see all the mega stones locations.
This one is found at night. Go inside Glittering Cave and take the first right. The stone will be found at the dead end.