This dragon is now limited (as per goal). When the timer runs out you will not be able to breed or craft the dragon.
Craft= 24hrs
Incubation= 16hrs
From Teamlava's blog:
This glimmering, multi-faceted beauty has strong loyalties to its Caretakers (so long as the Firapples continue to flow!). Craft the Amethyst Dragon in Dragon Story and watch your Island sparkle.