The Mystery Block is a block resembling the ? Blocks from the Super Mario Brothers series. It can drop up to around 50 gems when broken.
Mystery Blocks do not drop seeds, neither does its trees. However, Mystery Block seeds are available from a special random Special Event similar to Crystal Block seeds. Four Mystery Block seeds appear in the world, and players are given 60 seconds to search for them before they disappear. The event was not timed until the Crystal Seed event was officially added.