Hey,
At first started using a black velvet background, then switched to grey velvet, then went to black formica, and now am setting up a new booth using T.V. grey paper which is what I believe to be the stuff the pros that are getting the shots I want are using, or at least very similar.
I have used an aquarium flourecent light rigged up with two sheets of white paper and one strip of black paper in the middle covering it, to simulate two soft boxes up until now, but am moving towards the set-up with better lighting and reflection. Still learning in that department.
The formica that is in my current set-up is black from Home Depot. I have linked a photo below using this set-up to get into a marble I made that has to be seen into to be apreciated, as does most glass, and I imagine rocks to be the exact same thing. In effect they actually are the same thing. Again, this is my current set-up, and if I liked eveerything about the way it works I would probably not be here trying to learn how to get better myself...
Also with glass at least, you do need some kind of reflection or it just doesnt look real, for me it is trying to control where the glare is, how much of it is there, and what shape it is... Anyhow, here,s the link...
http://daysbetweenworkshop.com/glitterorb.html
...............Bird