These and many other "Crushed" gems drop in abundance off Frosticubes, frost spikes, and avanlance golems in the frozen sewers of Icewell keep. I was easily able to solo these light blue mobs with my 62 mage and my Ward of Xegony (air pet).
I wouldn't recommend making your entrance through the well in Icewell however, since the king often knocks unsuspecting adventurers down the well and the king and his hordes then turn on you for attacking the sewer mobs. There are entrances from Thurgadin as well as Great Divide that are safer.