The Aurora Stone was possibly the largest crystal in existence in a refined state; at one time, it was placed in beacon tower on Terra Atmosia. It was stolen by Master Cyclonis to power her Storm Engine though later destroyed by Aerrow to save Atmos. People from Terra Atmosia managed to pick up the remaining pieces of the Aurora and place it back in their tower, but getting the shards back was no easy task. The shards were almost stolen by the Raptors but Storm Hawks managed to retreive the shards.
The Aurora Stone was shaped basically like an egg with its colour light blue at the pointier and becoming a darker blue closer to the bottom, It also pulsed with white energy like all other crystals. The people of Terra Atmosia had also added a metal case shaped like a wing to it though this was knocked off when the Dark Ace used the Stone for his energy sword to destroy most of the Sky Knight Squadrons Skimmers.
The Aurora Stone is basically just an all powerful crystal though it seems to have some control over the weather like when the Stone was on its Altar in the Beacon Tower the weather was sunny with slight white clouds and when it was removed it became dark and stormy and that Master Cyclonis wanted it for her Storm Engine and not a Infinity Stone.