Obviously we can't see this in person and only have your pictures to go by. You say it is not glass -- you have it in your hand and can touch it, turn it, tap on it, scratch at it, etc. -- all things we can't do from over the web. From my end I really do think it looks like the very first picture on
this Wikipedia page.
Having said that, I understand it can be frustrating when you're pretty sure about some aspect of an object and everyone disagrees. Sometimes you really are right even when people insist you aren't. As an example, one time I posted a green rock I found at a lake to get it identified as I hadn't seen too many green rocks before. As I recall I had more than one person tell me that, of all things, my rock wasn't really green but probably just was next to a lawnmower at the wrong time, or else had stains from vegetation or algae or something. I ended up having to hit the rock with a hammer to break a chunk off to prove that, yes, it really was a green rock:
View attachment 1513061
Anyway, I guess my point is, sometimes on the other side of the internet, it's hard to see what is otherwise obvious in person when you can touch the object, manipulate it, do little tests, etc. To me it looks like the picture from the Wikipedia article I linked, but then, maybe if I was there with you it'd be obvious that I was completely off. If that's not what it is, I've got no clue. If Tamrock says take it to a gemologist, then I'd say I'm not going to be a lot of help. There are lots of places to find professionals to look at it, like jewelry stores, museums, etc. One thing you might have luck with is stopping by a local university and going to the office for their geology department (or equivalent). You may very well get lucky and find a professor or graduate student who's eager to help. I find I have had good luck doing stuff like this. A lot of times, people in academia don't often get to apply their skills outside a teaching environment, so when someone contacts them soliciting their expertise, they're excited to help someone who is interested in what they're interested in. For example I've contacted a GIS department asking about aerial photographs and got some that aren't otherwise publicly available. They were much better than Google Earth. I've also contacted a history department about whether they had a professor who was an expert in a particular topic -- they did, and he was quite happy to give me a reference list of materials on the topic I was inquiring about. Not everyone will be so friendly of course -- after all these people have jobs and responsibilities to take care of and may not have time. But the worst that can happen is they tell you "no". So, I recommend giving it a shot.
Just my two cents.
-mcl