As you know, man-made materials normally give off an unpleasant smell. Ivory can give off a very distinctive smell of burning hair, but because it is quite a hard material you may need to get your nostrils up close. Years ago I had a piece and it took several attempts before I picked up that dentist drill smell (my olfactory gear isn't as keen as it used to be), I wanted to know whether it was ivory because if it was I didn't want to keep it (just a personal thing).