Most common gall bladder stone is?

Cholesterol REF: Harrison's 17th ed chapter 305 Gallstones are formed because of abnormal bile constituents. They are divided into two major types: Cholesterol stones account for 80% of the total, with pigment stones comprising the remaining 20%. Cholesterol gallstones usually contain >50% cholesterol monohydrate plus an admixture of calcium salts, bile pigments, proteins, and fatty acids, the latter in "brown" pigment stones. Pigment stones are composed primarily of calcium bilirubinate; they contain <20% cholesterol and are classified into 'black" and "brown" types, the latter forming secondary to chronic biliary infection.