So usually there are cholesterol stones by cholesterol which is nothing but the fat kind of thing which is present in the bind and that may precipitate in the formation of the stones. Or it may be black stones because of the rupture of the red blood cells. Or it may be mixed. In India mixed stones are common. And it happens because the gall bladder is not working properly or the foods where junk foods not taking water properly, not doing exercise or not doing, or not taking fiber then. So, these are the major causes of the formation of stones at a younger age. So, gallstones may form in young people, middle people, or elderly people.