Yes, they are fairly rare, since you need to be winning a chest and then it needs to be lucky and upgrade, but if you are doing lots of resets of the world and seeing lots of chests, then you can see a fair number of Jeweled chests. You also earn Rubies from completing Objectives, Daily Quests and Missions, and can use those to purchase Jeweled chests.
 "Crusaders of the Lost Idols"){kind=icon}
 "Paladog"){kind=icon}
 "Cube Escape: The Lake"){kind=icon}
 "Theme Hotel"){kind=icon}
 "Supermechs"){kind=icon}
Congrats! And thank you. :)