There is quite a bit of noise (speckles) in the background. I think that makes the photo less smoothe than it could be, which takes away from the smoothe jems.
I disagree with having less forground. I like the reflection of the ring, and would not like to see that cropped out.
The focus and clarity are really good, and I like the detail we can see in the ring, and even the scratches in the table.
Lighting appears to be ok, but maybe need a little more in the background? I'm not really sure exactly what causes noise, but see it usually in areas that aren't quite lit right.
I also think that a different background color would work, as there really aren't many secondary colors in the shot. While there are a few traces of green, I don't think that the photo is ABOUT the color.
I like the setup, the angle of the ring is good, and the framing/cropping is good as well. I like the crop at the top, because if you added more room at the top, you would have your subject right dead center of the photo, and I think that wouldn't look quite right.
I like how you have the main green jewel in the front and the little jewels in the background for support.