I dug out the strand collected by Michael Heide, described in my notes to the blog post on Russians. In the blog post I compare them to the beads found in the Diakhite burial jars in Senegal (a faceted opaque blue similar in color to the interior layers of the Heide beads).

The Heide beads are 7-sided, but otherwise correspond well with the calcification and layered glass colors displayed by the 8-sided beads.

Re-inspecting the 8-sided beads with a loupe and penlight, a couple of them display an outside layer of the opaque "Dutch"/"Copen"/cornflower blue, a highly unusual occurrence, I think.

I'm familiar with the Mexican beads, there is no way the 8-sided multi-layered beads are from that production. Their comparatively less skilled cane drawing, and their calcification, seems more likely to possibly fit them into the category of the mysterious "loquis" beads used in the slave trade, of which I suspect the Heide beads may also be an example.

https://drive.google.com/file/d/0BxV1r8SUXxUwTmROeXpieER4UW8/view