Gems are collection items that are gained from dungeons and chests.
Currently the only use for gems is to sell them for cash or use them to replace gold in trading (Gems can be sent to other players whilst gold cannot).
Sapphire[]
Worth 100 gold. Can be found in chests and Level 1 dungeons.
Emerald[]
Worth 500 gold. Can be found in chests and in the later half of level 1 dungeons.
Topaz[]
Worth 1000 gold. Can be found in chests and in Level 2+ dungeons.