Hi Ciosi,
Do you mean fossilised mammoth ivory? I’m a bit out of touch with guitar paraphernalia, but I recall that being discussed some years ago.
Basically, denser material absorbs less energy than lighter material. So a denser material should improve volume, tone, and sustain. Most fossilised mammoth ivory will be more dense than most bone. Though, it doesn’t always make a guitar sound better.
I think it’s worth a try if you can find some legitimate material. 🙂
Daniel