I have a 70 series I shoot with elephant ivory on it. Doak once a year in mineral oil.
You asked about mammoth ivory which I understand to be fossilized; hard and brittle. I agree with elephant ivory being no problem with stress from recoil. I shot my SAA once with pearl on it and promptly got a chip at the conjunction of the frame and backstrap. Pearl is hard and brittle too. I don't do that any more. I don't know if I would risk the fossilized mammoth being pliable enough to absorb recoil. I think most of the replies above were for elephant ivory....anyone shoot fossilized ivory?
Any glue you'd like but nothing will work. Ivory expands and contracts and will ultimately break the bond. Perhaps Terry can suggest a flexable adheasive that doesn't harden.I shot my 1903 Hammerless with really old ivories on it. When I went to change grips the next time my ivories came off in 4 pieces. Seems the ivory backers were glued on and both sides popped right off. I'll have to glue them back on someday. I've been meaning to ask around here: What's the best glue for that? To glue ivory to ivory?