I am no expert on the subject. There are a couple of observations I could make (please correct me if I'm wrong):

1 - many, if not most ivories will have a nerve hole near the center of the chip (see chip below). If not an outright hole, then possibly a brown spot where the nerve hole would be.

2 - If you see flecks in the chip in a concentric pattern, it just might be walrus ivory. Flecks in a linear pattern might mean it's bone

3 - Absolutely clear white might designate celluloid or french ivory. However, there is a chance it might be elephant ivory.

Take a look at my website. I have 395 examples of real ivory:

http://www.angelfire.com/extreme/chipper/IVORY/IDcreatures.htm

Finally, and most importantly, when you get to the convention, make sure you stop by Dale Seymour's table. After all, he wrote the book!!