The hardness of bone is primarily due to a combination of collagen and crystallized salts. The salts include small amounts of sulfate, fluoride, and magnesium hydroxide; medium amounts of calcium carbonate, and large amounts of: Solution Bone contains large amounts of hydroxyapatite, which gives strength to the bone and responsible for its hard nature.Its chemical compoistion is Ca10(PO4)6(OH)2. Usuallay bones conatins high amounts of mineral salts of calcium, phosphorous and magnesium..