Pork bones (hocks) were dried and burnt in a wood stove. The color of the burnt bones ranged from white through grey to black with "tarry substances" visible by a naked eye. The body of the burnt bones consists of calcium phosphate with some unburnt carbon. Calcium phosphate may be used as a fertilizer. This SEM image was obtained inside a bone joint. Enhanced SEM. Image width: 3200 micrometers. Magnification: 31x if the image is printed 10 cm wide. Bar: 500 micrometers.