the appearance of material is ancient, I think it's authentic, islamic and gorgeous!!
It's definitely not a Jatim (wrong structure).
I think it's almost certainly an authentic and very nice late Byzantine or Islamic bead. However, I'm just a little doubtful because of the air bubbles in your close-ups. Not the presence of bubbles themselves - most ancient glass has a lot of bubbles, both internal and in the surface - but the consistency of the bubbles in the white glass reminds me of the artificial surface treatments in some of the recent fakes made in Java (see the first attached pic). But, of course, that sugar comb effect (it reminds me all too temptingly of the candy I was addicted to as a child in the UK!) is seen quite frequently in ancient beads, including Jatims (this little bead that was found in the Philippines, for instance), so I think you should overlook these lingering doubts. Yankee would know for sure.
would be replicas. I am not experienced or anything near an expert in this type of bead, but I have been learning from all of you who are. There is something too perfect about this to be authentic & truly aged. Look forward to hearing answers from those who do know, rather than my hopeful guess based on what I've learned from Beadcollector! Thanks, Lynne
Somehow the bead look bluer in the flesh, I do not know why on the photos the whitish eyes stand off.