Popcorn texture is a term for a macro-texture observed on exposed and weathered clay surfaces commonly associated with deposits of sodium bentonite (usually on open-pit mine-faces, bed outcrops, or stockpiles). These high-swelling bentonites develop irregularly rounded lumps resembling mounds of popped corn caused by successive periods of swelling and shrinkage from the cyclical uptake and loss of water within the clay.
See also alligator skin texture.