Mastodon Ivory is an interesting material...it is ancient and can have some interesting and beautiful colorings. It is also not on the "banned" list.
You'd be surprised how much "ivory" is available in a decent sized tusk...literally pounds and pounds of the stuff.
I was a Scrimshaw artist back in the seventies when it was very popular and rather easy to get...I still have a rather large collection of ivory "blanks", sperm whale teeth...more rare...etc. Back then it was getting hard to acquire due to the rules and regs but doable as long as we were getting it through "approved" dealers, which we were.
They, ivory and sperm whale teeth, are beautiful materials to work with. They are rather dense, take a wonderful polish that allows for engraving and age to a magnificent color as long as exposed to light. My collection has been in darkness since the 70's and still look like the day I stored them away.
I've seen Mastodon Ivory used in knife handles and they are beautiful though I'd not use the knife as a beater.
Here are a few images of my stuff: