Trading Portal gave a small quartz for a Virtue Dragon
I traded in a surplus Virtue Dragon but only received a small Quartz. Based on all of the sources I've checked, the Virtue Dragon is a rare dragon.
Isn't the Trading Portal supposed to give large gems for Rare dragons? Or does it require super rare dragons to get large gems?
To get large gems you must trade super rare dragons
Yes, there are always exceptions to the "rule". When you initiate a trade, the app will show you what you will get in return. Always check this to know if it's worth trading (or even feeding up your baby). Bear in mind sometimes the game won't actually give you mystery box items though (I think Mystery Box options includes "nothing" ).