As mentioned previously, as with your bead, this is a finished object. If the intent had been to color and/or decorate it, this would have been done (most likely) prior to drilling.

But, in any event, I don't know what the material would be. Since it is agates that take the coloring and decorating processes, and I don't know if this is an agate bead, I'm not in any position to give a reasonable reply.

The owner says this is the largest bead found in ancient India. I'm not confident this is necessarily true. But it is certainly a very large (long) bead.

Offhand, I cannot say I know any art or iconography that depicts Indians wearing big stone beads from ca. 2000 years ago.

Be well. Jamey