Here's a bead I can't figure out. It looks like the hole has been partially filled with what looks like ground glass which was fused. Possibly this was done to repair the bead since there are a number of cracks that may go all the way through. Initially I thought the grey-ish stuff in the hole was sand that could be removed, but it is fused or otherwise bonded into a solid hard mass.
One side of the hole has a lot more of the different material than the other, as shown in these two views.
Is this a repaired Islamic period bead?
Note: The diameter is 15 mm and hole is 3 mm.