When a body is cremated, it's burned at about 1500 degrees F. in an oven called a "retort." The head and the heart take a long time to burn. Gold and mercury fillings vaporize. After the cremation, there are a lot of bone fragments left, most of which get tossed out. The rest of the cremains (a great word!) get tossed into a big blender and are pulverized into a fine powder.