It's about and inch by an inch and half. No it's firm.. not as hard as stone though. The green outer feels like glass.
What’s the back look like? The front looks like it’s a jade decorative object, I suspect the centre is missing and what you’re seeing is where something was mounted.
I'd hazard a guess on it been a type of bottle/ jar top which would have had cork fastened to the bottom of it
Get a really bright light & shine it from behind, see if you can pick out any detail. Maybe that centre is Opal, there a few ways of telling if it's Opal or not.
No Idea what it is but your palm lines point to a long and prosperous life with a career change imminent