I think you are really wondering about cut glass, as in clear cut crystal, like the old school decanters and such. Something like this, but a bong of course:

https://www.steuben.com/product/tortoise-ice-bucket

Sometimes they are called coldworked glass as well. I have seen people make them. It's just a time consuming pain in the ass to make and thus, very expensive. Plus it takes a shit load of practice to get good at it.

Yes, they are leaded glass. No they don't leach lead into the bongwater, no they are not dangerous. That has been repeatedly disproven.

https://www.chicagotribune.com/news/ct-xpm-1989-02-05-8903030646-story.html

Leaded (and sometimes Barium) based glasses have a certain reflective quality when they are cut that makes them brilliant to see. But the type of glass is thick and is much harder to work with than the common bong material glass (borosilicate). Plus the slide would still need to be boro since the leaded glass would break from the heat of the lighter.