Here are a couple of photos I took already for something else I've been writing. One is of a slightly unusual red green and yellow twisted bead - medium size, about 15 mm. The other is of a larger bead (similar to one of yours, Hendrik), which was found broken. It seems to have been lying in close proximity to some iron object, which had completely disintegrated over the intervening fifteen hundred or so years. I don't know enough about chemistry to know if the iron might have contributed to the breakdown of the glass. In any case, the fragment gives a good idea of the structure of these beads and of the almost porous quality of the glass in the core.

Cheers,

Will