X-Ray Diffraction analyses made on Neolithic beads from Sudan have identified them as Natrolite, a silicates aluminum and variety of Zeolite. Does anyone know any analogy please? And where are the sources of this material in Africa? Many thanks!
After a quick search, I found reference to natrolite beads in a 1973 issue of the Nyame Akuma newsletter. Please check the link for downloading the pdf below. Hope it helps!