<prompt> Black bile stones are composed of:Calcium bilirubinate stonesCholesterol monohydrate stonesCalcium monohydrate stonesCholesterol bilirubinate stones  <response>: There are cholesterol stones and pigment stones. Cholesterol gallstones usually contain 50 cholesterol monohydrate. Pigment stones are composed primarily of calcium bilirubinate; they contain 20 cholesterol. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Pages 2616-17 