I picked up a Woolly Mammoth tooth while in Alaska this spring.
It was a really old, gnarly, piece and I have been experimenting with different techniques to make a pen out of it.
The first two attempts failed miserably as this material is very "crispy" and doesn't have the ability to bind - regardless of how many ways you can come up with to cut it into blanks.
I was able to get three other pieces to the stage where I was able to drill.
The first one totally disintegrated, but the second one held together very well - probably due to several choices (guesses) I made in the approach and method.
Working with "brittle but rock hard" material is a challenge, but here is a photo of what I produced - and it doesn't do it justice. The thing is breathtaking and I will be working on piece #3 soon.