The original post slid to the second page, so I'm re-posting the original pix.

I heard back from the cement expert and David wins the prize - the beads are made from Portland cement, with a paint that contains iron - presumably to tint it coral pink.

I'll be looking into the history of Portland cement and will probably publish the analytical results from Dr. Ted Sibbick in the Bead Forum newsletter (twice yearly from the Society for Bead Researchers - join today if you are not already a member!).

And thanks Jill (jrj on the forum) for the suggestion to contact the cement industry!