I think you're right. I was trying to separate it from the edges of the gem, so as to give it a little more of a cut look, but it winds up looking like it sticks out a little. Maybe toning the green down in the middle will help.
The gem looks nice. I think the highlight in the center is unnecessary though. It makes it look like that the inner lighter shape is protruding straight out. Maybe it's just me.
The top seems a bit too light