Hi there
Jamey posted every thing about jet beads.just i have to add some points.
Afghanistan became separated by from Iran in 1857 when British attacked sout Iran .so some times it is difficult to say a bead is from which one.like banded agate from Bamyan in north Afghanistan which we see a lot in Iran.i have been looking all around Iran for old beads.but what i found there are connections between the time of British in sout Iran and trade beads.i didn't see any type of chevron or Venetian beads except sout Iran near Persian golf.also many jet beads over there some times different
shape by those antiques which i seen. so European jet could be candidate found in Iran.although turkish jet is first candidate since old time.
Afghanistan has its own beads and pyshavar was a famous market for old Afghanistan and Persian beads.if you heard Gabri beads it means beads made by fire worshipers[ZOROASTRIAN).Thats how they used to call them in old time in iran.so mostly glaas or ceramic beads BC or to 6 century they call gabri beads.there are two different stories about jet beads among nomads here.first for protecting shepherds in dark nights.two making increase in couples love and loyalty .just remind it as fun .
my jet beads are light and shiny and i wear them individually.
all the best
Ali