On my about me page (
http://members.ebay.com/aboutme/antlercarv)
I have a link called: Ivory info and laws, that gives info on various ivories and ivory substitutes and how you can identify them. Bone may or may not have a visible grain. Ivory may or may not have visible grain. If you see a cross-hatch design, in the side (thin) part of the button, you may have ivory or fossil ivory. The cross-hatch is called Schreger lines. If the button has visible porosity along the back of the button, it is probably bone. Send me a picture, and I will give my opinion. I have carved hundreds of pieces of bone, antler, and fossil ivory.