I wish I knew more about the technology of bead-making through the centuries and by different people! This is canes on a core of non-uniform green with subtle swirls of lighter and darker glass. It sort of looks like it was broken, though there are no obvious signs of the break - I'm guessing they were ground down in modern times; there are smooth areas, when most of it is very pitted. I'm also guessing the hole is modern - small (~1.5 mm), uniform and straight.

Just a chunk of well-weathered 19th C Venetian bead, or something else?

Thanks again for all your help!

Kristi