The Sapphire isn't the gate.
Especially since Dorukan built a self-destruct into his own gate defences. The possibility of bad guys gaining access to the gate and using that to do evil things was a known risk, and the epic wizard's solution was to make sure the gate could be destroyed before letting it fall into enemy hands.
Well, we know the basic locations of all five gates and have a rough sense of the geography. Most of them are in the wilderness with the exception of the Azure City rift, and the Redmountain and North Pole rifts both seem to be located underground.