"Athame" is a wiccan word, and their ceremonial daggers are usually made of wood or metal. What you have or are admiring is a ritual knife or dagger, or we can just say "blade" to simplify it.
The type of bone is important because the bone is a connection to the spirit of that type of animal and its associations. When working with bones, you are working with the energy of the kind of animal the bone belongs to. By using parts of an animal in your magick and bags, you are utilizing the power of that animal (symbolically).