And this is all precisely why I am obsessed with what silver, glass and heat can do together.

I've always been sure Chalcedony involves silver. I've never managed to get my hands on any really old stuff though. I found some new stuff when I was in Germany, made in Alexandria by Ahmed Fouad, perhaps about 10-15 years ago. His chalcedony stuff doesn't seem to appear now.
I did a bit of a search for him, and found this thread. John gave me the little Hebron posy in question. (thank-you again!)
https://www.glassmessages.com/index.php?topic=53544.0