The sources of Roman imperial glass are all in the hafnium

[gallienus1]

Romans distinguished between two types of clear glass: Alexandrian and Levantine. It appears that research using the hafnium isotope content of the glass indicates the Roman understanding of the origin of the different types of glass they used was correct. A case of ancient writings confirmed.

See-

https://www.sciencedaily.com/releases/2020/07/200709105112.htm

and-

https://www.realclearscience.com/quick_and_clear_science/2020/07/13/where_did_romes_famous_alexandrian_glass_come_from.html

[mix_val]

Great info!   Wish I still taught the chemistry of arts and artifacts.  Would have made a good lecture!