Can anyone identify this Emerald Green Stone?

[mainemomlooking]

  

Found this in the bottom of a jewelry box that I purchased at an estate full of antique/vintage jewelry and a Gorham trinket bowl.  Question is, I dont have a clue what type of stone it is.  I have backlit the piece to show you how the light shows through.  The piece has no marking and is open in the back.  Help 🙂

[mainemomlooking]

here is the picture without being backlit

[volemus]

You will probably need to get it tested of course; but what this reminds me of is one of those way-oversized stones selling out of Asia years ago that, IIRC, were made of cemented bits & pieces of the genuine gemstone? Honestly can't remember what the deal was with those.... They sold for like $5 or $10.

Photo details are fuzzy, and I'm certainly no expert anyway but this doesn't really have a look of something old, to me.