no known origin,its opaque its 2 1/4" leaves no streak, has a hardness of 6-6 1/2 I drilled it with a diamond plated bit,it is a very tough stone.It weighs 2ozs 56.6 grams.When I drilled it the powder from the hole was whitish, afterward it was the same green color right through the hole.I was not able to determine its density.This stone is not magnetic.Has some very thin dark lines that are on both sides. ]3]3
Without anymore information, best guess is that your rock is metamorphic quartzite based on texture and color. Does the rock feel about the right weight for its size? If yes, that would also suggest the rock is a quartzite.
Other possibilities: Jadeite - Usually translucent and somewhat waxy luster. Not a good match for your rock. Amphibolite - Can be dark in color but typical has a more grainy texture than your rock. Serpentinite - Minerals that compose serpentinites are more dense than quartz (specific gravity 2.65). These minerals have specific gravity > 3.0