In DragonVale for the Android & iOS devices (iPhone, iPad, etc.), the Jade Dragon is a Gemstone Dragon that isn’t tied to a particular month, and seems to instead represent all Gemstone Dragons.
The Jade Dragon has a base breeding time of 30 hours 26 minutes and 15 seconds, sells for 2,500,000 coins, and earns 150,000 XP for successful breeding once you reach level 14.
To get a Jade Dragon, you need to breed a Salamander Dragon with a Plasma Dragon.
Check out my DragonVale Breeding Guide for more dragon breeding combinations.