Regarding your bead, I am pretty sure it's from Persia from the Seleucid period,300-200 BC. Seleucid was one of the generals of Alexander the Great and when Alexander died, the vast territory that he conquered was divided in between all of his army commanders. Seleucid got the chunk of Persian region. You can see a very strong Greek influence on the shape of the bead. They used to have lots of buds, acorns, etc…
The bead in the photo is upside down. The bottom part , which is the widest side of the perforation, probably had a gold cap on it. It was one of many identical graduated ones. Judging by the size of your bead, it was probably the center piece or close to the center.
I have seen a half necklace with the gold caps in Jerusalem but it was not for sale.