They are calcium like accretions that form in the bile ducts leading from the gall bladder to the small intestine. The two types of gallstones are cholesterol stones and pigment stones. Cholesterol stones are usually yellow-green and are made primarily of hardened cholesterol. They account for about 80 percent of gallstones. Pigment stones are small, dark stones made of bilirubin. Gallstones can be as small as a grain of sand or as large as a golf ball. The gallbladder can develop just one large stone, hundreds of tiny stones, or almost any combination.
If any of these ducts remain blocked for a significant period of time, severe�possibly fatal�damage or infections affecting the gallbladder, liver, or pancreas can occur. Warning signs of a serious problem are fever, jaundice, and persistent pain (Source: National Digestive Diseases Clearing House).A surgeon friend says that surgical removal of the gall bladder is still the most common treatment, but I'd want a second opinion...