what are gall stones
Gallstones are pieces of solid material that form in the gallbladder. These stones develop because cholesterol and pigments in bile sometimes form hard particles. The two main types of gallstones are: 1  Cholesterol stones: Usually yellow-green in color, approximately 80% of gallstones are cholesterol stones.allstones form in the gallbladder, a small organ located under the liver. The gallbladder aids in the digestive process by storing bile and secreting it into the small intestine when food enters.