When mineral levels in the blood are too high, bones absorb some of the minerals and store them as mineral

This process is known as mineral homeostasis.  
Simply the correct level of calcium is required in the blood, in addition to different minerals, for the body to work regularly. Bones retain a portion of the minerals and store them as mineral salts, when their desired level get way past the normal. when their level shot below the adequate, bones discharge a portion of the minerals once more into our blood making sure that homeostasis is at the level that it's supposed to