The only part made of stone has no moving parts. All the moving parts are iron or steel. I notice he has no lead screw or even gears. I suppose stepper motors and cnc have replaced most of the tricky bits.
Reminds me of the glass snowboard someone had made. It worked okay until it didn't.
Bill D.
https://www.youtube.com/watch?v=vmZ1QfZ9Skk
5:00 they start to ride.