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.
Yeah, I assumed it would be glass since they're set in silver rather than gold, but I've seen some rings where a small ruby or sapphire were set in a Sterling ring. For the price, I figure it'll help me avoid throwing out a real stone at some point.
!BBH
!PIZZA
!ALIVE
Like you said, you can never know until you really look into it.
Some of the most valuable (expensive) stuff from the Victorian age is costume jewellery.
And Cubic Zirconium, almost exactly like diamonds, except it doesn't dissipate heat like a real rock.
So, keep testing.