In DragonVale for Android and iOS systems (iPhone and iPad, etc.), Jet Dragon is a Gemstone Dragon which represents multiple birth months, spanning from the middle of November through the middle of February.
As a Gemstone Dragon, the Jet Dragon earns gems instead of gold and can not mate at all.
The Jet Dragon has a base breeding time of 30 hours, sells for 2,500,000 coins, and earns 150,000 XP upon successful breeding at level 11.
To get a Jet Dragon, breed an Ash Dragon with a Frostfire Dragon between the middle of November and the middle of February.
Check out my DragonVale Breeding Guide for more dragon breeding combinations, as well as the combinations you’ll need to make the necessary dragons for the Amber Dragon, and other Gemstone Dragons.