thank you very much for the detailed info!
Now having read a bit on the net about >> Cryolite glass
, that certainly seems to be the material used in this paperweight.
(I still haven't quite understood if it is really the same as opalescent glass -- would that be distinguished depending on which additives are used?)
I think the glass itself doesn't have a colour (you may be right that the glass has darkened with age), all the colour effects appear when looking at the weight in different light situations -- quite fascinating. And the simple and not very well executed flower looks much more interesting in the mist
Maybe the paperweight comes from an area in Bohemia / Czechoslovakia where glass jewelery was made, like Gablonz -- they seem to have used opalescent glass frequently for beads.
Unfortunately, I don't have a UV lamp at hand atm, but will try to borrow one.
BTW, those Japanese artists produce some marvelous pieces...