Abstract: Transmission electron images of fine-grained micas in bentonites exhibit lath-shaped units. These units seem to be associated along the (110) planes—referred to 2M1 mica cell—with perfect registry of their individual lattices. In doing so, they seem to provide lateral growth in the (001) plane. These lath-shaped units are arranged in the  direction in modes similar to the stacking of layers in mica polymorphs. Aggregations of lath-shaped units with polycrystalline montmorillonite particles are also observed in several bentonites. From the SAD pattern these laths are inferred to be dioctahedral layer silicates. However, they cannot be exactly identified any further. It is an open question whether these laths have grown from the montmorillonite or are simply entangled with it.