Balancing stone from inner ear. Coloured scanning electron micrograph (SEM) of crystals of calcium carbonate on the surface of an otolith. An otolith or otoconium is a calcified stone that is found in the otolith organs of the inner ear. They are attached to sensory hairs, and, when the head tilts, the movement of the stones causes nerve impulses that form the basis of the sense of balance. In humans, otoconia can range in size from 3-30 microns (millionths of a metre) across.