Gallstones. X-ray of a section through the abdomen of a 48-year-old patient showing gallstones in the bile ducts. The patient's spine (white) is at right. Gallstones (choleliths) are most commonly hard deposits of cholesterol that form due to an imbalance between bile and cholesterol levels. Stones can also arise from bilirubin and calcium salts found in bile, which is produced by the liver and then stored by the gallbladder until it is needed.