I was asked to identify a similar strand of "beads" from Nigeria a few months ago. Unfortunately, I missed an opportunity to show them to my friend Si Frazier (a geologist and mineralogist), whom I hoped would confirm my suspicions about these things.

These "beads" are clearly organic in structure (made by a living being), but are composed of a concreted material (sand and earth bonded together to become very HARD).

That they might be pieces of termite galleries does not surprise me—though I am delighted to read this from an outside interpretation, since I could not have guessed with any certainty which animal (whether termites, ants, wasps, or whatever) might have made them.

I also tend to agree that the "beads" I saw appeared to be unused, and to have been strung-up to be presented as a "necklace"—though I would be inclined to doubt anyone ever actually wore them as such. I think they are something scavenged that is convenient to be strung and to become "beads." This can happen many places in the world, where fossils and other materials are recovered, that are already pierced (or a present-but-clogged perforation is easily opened). Crinoid stem segments come to mind--as does naturally-perforated amber. Though people DID collect and wear these things, in antiquity and even recently, this doesn't mean that EVERY specimen collected and offered has been so-used. It would be easy to pass-off these specimens as "beads"—but they may only become that once they are sold to us and worn by us (!).

Jamey