Yep, they look like glass, from age/petina of silver, it looks like the age they would make such things.
And it's that color red of glass.
And the corners do not look ground (the facets)

Also, from the design of the silver, the stones wouldn't be expensive. Expensive stones = expensive setting. Usually. (Your mileage will vary)

AND!! just to inform people. I have seen Tiffany lamps/windows… and thought, what crappy construction. Sometimes, you cannot tell.