Beautifully made. Is the material poured glass? The color reminds me of very, very weak tea. The back “glass” feels smooth but the front seems to “curve” in just a little bit. In second picture there looks like something above the clasp pin but that is something in the glass or goldtone below it. Nothing that looks like any kind of marking to me. Not noticable to the naked eye. Key words? Description?
I'd be checking super carefully for a faintly stamped sterling mark, use a loupe if possible because it looks a bit like vermeil ....
You are the only one who can tell if the material is glass or not ....not having the item in hand means we can't tap it against our teeth, feel the temperature and examine it with a loupe for air bubbles which ones sees in glass ... all those fun tests joolies perform on our items. 
The material could well be lucite ..... it sure reminds me of jelly belly jewelry, which used lucite to such great effect.
I agree this is a very nicely made brooch.
Thanks to both for your help and knowledge!!
I haven’t found any markings yet. No sterling 
I do now see what looks like bubbles. I first thought the cold I felt on the front was from the “gold ribs”. I now think everything is covered with “glass” on the underside and the top except the very outside of the brooch and the center that the stone is in. If so, would this be called “poured glass”? Still looking and hoping.
I really appreciate this board. I have so much to learn.
Thanks, mainemomlooking, for doing some research and for your response
Its funny because, I don't wear much jewelry - and I don't know much about jewelry - but I love to find pretty piece - and this is a very pretty brooch. Looks even better than the pictures.
I may end up keeping it (for my collection) or giving it to a relative or friend I know would wear it. I am not even sure I could give it a good title and descripton, if I tried to sell it.
