These summons state in their description that they are nothing more than a crude floating rock. This floating rock can get poisoned and sneak attacked in its vulnerable softer rocky spots, but most amusingly it can be charmed and confused. It is funny though watching the rock bowing when it is confused but I'm not sure rocks are meant to. It may be better for the floating rocks to be considered as little elementals.
Also on the theme of the Earth Elemental summonins, changing the second circle summon to an improved version of the first would be awesome :)