Over 3/8” (0.41”) length, faceted cubical, possibly aventurine. Drilled from both ends and showing natural cleavage. Aventurine was principally worked in India at the time and traded over a large area, at least to north Africa, and possibly to the Baltic hinterland. As Vikings are known to have raided Mediterranean coastal towns and capture slaves which were then sold in north Africa, that is likely the source for this bead.
