Apparently the nut's on those are Bakelite - which is actually the very first plastic ever produced. Commonly found on old saucepan handles and kettle plugs. It is very dense and can be quite brittle - which makes me think its probably a lot more like bone in the way it behaves than a cheaper ABS nut. The ABS is a lot more malleable and would absorb vibration more than transfer it. Which seems to be the point of using a hard material like bone/brass/graphtech.