A great many 19th c billiard balls were manufactured out of mammoth ivory. And no, I don’t have a citation for that. :’)
I wouldn’t be surprised. There’s an astonishing amount of mammoth ivory raw material available. Especially now that other forms of ivory are largely illegal, and mammoth tusks keep being found all over the artic in the U.S., Canada and Russia... It may not be exactly plentiful, but it is available. If you want a set of mammoth ivory grips for your Colt 1911... They can be found without much trouble.
The big difference is the quality of the ivory. Most of the mammoth ivory is yellowed, or has harsh grain, stains, and lots of marking in it. Dark stripes from cracks are common. What attracted me to the knife was the pure white ivory. In mammoth ivory I’ve seen, that’s fairly uncommon. That tells me they had a pretty special sample from which to make their handles.