The DLC achievements. Do the following to unlock.

Unlockable	How to Unlock
Blue Gem Hunt (10)	Collect a blue gem in Marble It Up! multiplayer match.
Map Pack Dominator (20)	Get 40 gems in any 3 of Playground, Bowl,Concentic, Vortex Effect, Blast Club (Marble Fu pack).
Master of the Spires (20)	Collect 50 gems in Spires (Agroaphobia pack).