OK, so we've determined it's glass...

While photographing these Czech glass beads today I was reminded of your bead. These are 8mm beads with a hole that will accommodate a 1mm leather cord (that is, a larger hole than most Czech pressed glass beads).

These aren't old beads; their nice satiny look is due to the type of glass and a semi-matte polish.

Note the mold line around the equator, which is what made me think of your bead.