Setting the tube rivet

Fit the tube into the hole of the stone and using a small round punch, gently tap one end to flare the top. Turn the piece over and flare the opposite side slightly. Keep alternating sides, using progressively larger dapping punches, then the round side of a chasing hammer to completely flatten the rivet against the stone. Use care not to chip the stone.
Sand the rivet smooth, but do not sand the stone.

Sanding smooth.