Bone contains living cells and organic matter such as collagen, protein, and polysaccharides. However, much of the volume of bone is made up of minerals, which may comprise as much as 65% of bone mass. Calcium and phosphate are the most common minerals, with calcium in the form of hydroxyapatite and calcium carbonate. Magnesium, hydroxide, fluoride and sulfate may also be present. Where do you think the body gets the needed minerals?