After many fails I now have my Aquamarine breeding in the Island. I will keep trying for my display egg too. Sadly, I will have to get rid of one of my three Pearl dragons, as they are taking up the space I need for the new ones. (for some reason, I was insanely lucky at breeding Pearl, so I bred two extra to earn me gems while I waited for the rest of the Gem dragons to come out.)
Good luck, everyone!