A spectrum of spherical grains ranging from spherulites through oolites, pisolites to grapestones, formed at an average temperature of about 8 degrees C, were observed in a fresh-water dam foundation drainage pipe. These low-magnesium calcite spherical grains each have a thick cortex with or without a nucleus. The cortex is characterized by concentric laminae and fibro-radiating rhombic to sheetlike fibrous crystals. Nuclei have coarser crystals than those in the cortex. Calcium-rich solutions originating from foundation grout reacted with atmospheric. CO 2 to form these spherical grains. Nucleation and inorganic growth of these spherical grains appear to be related to the water-flow rate.--Modified journal abstract.