Two types of gallstones can form in your gall bladder; cholesterol gallstones which form if you have too much cholesterol in your bile and pigment gallstones which form when there is too much bilirubin in your bile. These gallstones tend to develop if you have liver disease, infections in your bile tubes or inherited blood disorders e. g. sickle-cell anaemia(your red blood cells are a different shape and this affects the amount of oxygen they can carry around your body).
Attribution: BUPA