When describing the workings of a germicidal tube (fluorescent-style), many people claim that the envelope is made of quartz to transmit UV-C. However, I have yet to see any molybdenum foil seals in any type of fluorescent or non-fluorescent tube. This suggests that (as I expected) they are just using high-purity soft glass, which makes a lot more sense since high temperatures or high pressures aren't involved.

Has anyone ever seen a quartz UV-C tube? I am not talking about high or medium pressure lamps, just low pressure fluorescent-style lamps.
 

Yes I have a couple of Soviet made F8T5 style germicidals in quartz. Also these modern tiny Chinese CCFL style UVC lamps are quartz made with foil lead-outs.

Quartz is superior, of course, but so are production costs, so it get substituted with uviol glass for mass made lamps.