A laboratory model duplicated the conditions necessary for pisolite formation in mines and caves. These are (1) supersaturated calcium carbonate solution, (2) grain agitation, (3) available nuclei, and (4) the presence of a splash cup. Calcite layers were deposited in the laboratory experiment. Growth rates of pisolites so formed were 1.5-2.5 times greater than the average accretion rate of 0.1-0.2 mm determined from pisolites of known age in mines.