Composition -- I feel that you have effectively used the composition of this subject to create a balanced shot. The marble placed in the right third allows the "shadow" to go to the center, thus directing the viewer's eyes into the picture. I think cropping it the way that you have is also effective in that you didn't try to fit the whole shadow in, which may have made it seem "top heavy." Excellent choice of subject, and it fits the challenge very well. The "background" material is also interesting. If possible, it may have been interesting to let the little "holes" lead the eyes to the marble.
Technique -- To me, the focus works well in this shot. I know having a blurry foreground can be distracting to alot of people, but here I think it really makes the marble "pop." The reflection in the marble is interesting, but I found myself trying to see what was above the horizon in the reflection (or below it, I guess). Would it have been possible to "curve" the background material up so that only that would be reflected. That is obviously a personal preference, because I can see how the reflections add some interest.
Overall Effect -- I felt that this was an awesome photograph, and a creative idea. The simple colors and composition are eye-catching, and the whole pic works well, I think. Sorry I can't offer more "constructive criticism" but this is a good picture, that does not need a lot of work, I think!
Like how the sphere picked up the pattern of the cloth it is on, and the pattern shows through the blue shadow. Nice cloth for a base, only thing is it goes out of focus to much to fast. Plain and simple and nice. Good job. PTL 7
Awesome macro. Good choice for the surface (is that a paper towel?). The round patterns work well with the marble without detracting attention from the focus. I really like that the pattern is reflected in the marble. It might be just a touch over sharpened.
Very nice, very blue! I like the composition and DOF. I would have liked the front edge to have been sharp as well. I'd like a blue crystal like this myself!
I know this is nit-picky, but the only thing I would have changed is actually have the marble exactly in the center of one of the paper towel rings. Nice macro otherwise.