Gem identification? Help please

[pcaspian]

Can anyone help me identify what stone this is? I got it from my grandmother who passed away. Also, can anyone help me identify if it's a genuine stone or not? It used to be set on a ring that had a 750 inscription in it.

 

[Bron357]

Unfortunately, not from a photo. It could be glass, synthetic something, green quartz, garnet, Tourmaline or even sapphire.
Take it into your local jeweller / pawnbroker, they can at least rule out glass.
Otherwise you’ll be needing a gemologist to do some testing ie specific gravity, refractive index etc to give you a correct and positive ID.
Large and very clean gems, even set in high carat gold or platinum, usually turn out to be a synthethic corundum or synthetic Spinel. Not worth much money but nevertheless a pretty and hard wearing stone.