I found this stone on my recent jobsite. Its pale green on 1 side (showing) and plain granite on the other. Its has small points of reflected light however i cannot see any definate crystallization within it.
If you’ve got a local lapidary club you could take it there. It looks like green quartz to me (also known as Prasiolite) and as is rather opaque it might be best to tumble it (just smoothing the outside surfaces) or having as a specimen.