what forms gallstones
Gallstones form from bile, the yellowish fluid that is produced in the liver and stored in the gallbladder until it is released into the small intestine to help in digestion. Bile is a mix of cholesterol, water, pigments, lecithin, and salts (electrolytes), such as calcium, that are kept in equilibrium. Gallstones form when one of the constituents of bile precipitates out and forms a solid mass that may range from the size of a grain of sand to several centimeters large.