Pisolites were being formed in 1936 during aeration of the water from the oil wells of the Luling Field, Caldwell County, Texas. The field is a faulted monocline. Production is from the Edwards (Comanchean Cretaceous). In the wells, the Edwards is porous and rotten with oil in its upper portion and water in its lower. The oil and water were produced together and separated in settling tanks. The water was hot, saline, carbonated, and saturated with hydrogen sulfide. This poisonous gas had to be removed before the water was discharged into stream floodwaters. It was removed by aeration. The well water was lead through pipes several inches in diameter to the top of wooden towers some 12 ft. high where it was discharged. Pisolites formed in the violently agitated pools on the floor below. The pisolites ranged from 3 mm. to 50 mm. in diameter, and their shapes ranged from spherical to ovoid to irregular. Their centers were irregular and usually surrounded by many thin concentric crystalline layers of calcium carbonate, probably aragonite. A few years after 1936 the method of aeration was changed.