Looks interesting so far. CR 15. The breath weapon is its traditional debilitating breath, which does thunder damage and can incapacitate targets (on a failed save) within the cone. It has some innate psionic powers (scrying, telekenesis, and teleportation circle), spider climbing and tunneling, and has a telekenetic fling and teleport in its legendary actions, all of which descend nicely from its 2e psychoportation and psychokenesis powers.
Also - a teleporting dragon once per round is terrifying.
Lair actions are basically charm, stone shape, and wall of stone (again, traditional powers for the type).
And there is a fairly extensive lore text, both for gem dragons in general and sapphire dragons in particular.