Netsuke I think, too.
But no idea on the material, it's very hard to determine that based only on pics.
Learnt something ne aswell, had never heard about an "ivory nut"...
well...the carving looks formulaic and rushed....no real attenton to detail...and the wire seems to be pretty standard too. I am guessing it has limited value so also made from a material of little value as well.
no not jadeite...no way. All jadeite is jade but not all jade is jadeite. Actual jadeite would be far too expensive for such a crude piece. Jadeite is a very specific stone and has far more value than nephrite, the other much more common form of jade. You see folk all the time in T-net and Ebay confuse the two.