Antique brooch?

I found this brooch years ago when I bought an old sewing box at an auction. It was full of old sewing supplies and some antique hat pins, and this was rolled up in a Kleenex at the bottom of the box. So I don’t know much about it other than it looks really old not sure what the stone is but it is a beautiful green color. The setting is two pieces and it was pretty grungy; almost brown. I just gave it a cleaning with a soft brush, and some mild dish liquid. It did clean up quite a bit. not sure if it is gold or something else… A magnet doesn’t stick to it . The green stone has some imperfections in it. It looks a little wavy with little lines.in it. I know very little about old jewellery so if anyone is able to help me with this, it would be greatly appreciated.. I can’t find any stamp or markings on it. It is approximately 1 inch Long, and a little over half an inch wide