I took this into photoshop and jacked up the levels and to me, it made the marble stand out a lot more by adding contrast. As it is, it seems a little flat. I think this is partly due to underexposure caused by the light background.
I did some marble shots, but went with a different subject for my entry this week. I love your composition in this image. The marble details are great, and the shadow really makes the photo. Focuse, DOF, and lighting are all perfect for the subject. My only complaint is the background surface seems a little muddy and flat. I don't know how difficult it was to get your lighting the way you wanted, but I would like this better with a brighter background. I still give it an 8 for execution, composition, and detail.
JD Anderson
Nice idea to include the shaddow (cool how the light is bent through the marble!) Nice composition, goes well witht the title. And the little bibbles in the marble are round too!