I think what I need to do is to get some light pointed downward, into the glass marbles. One the sample below, I had the bare sb600s firing into the glass at 90 degree angles..but I didnt really like the harshness of the lighting...so I siwtched to using umbrellas. The umbrellas dont light the rocks up enough though...No don't delete any. They show what can be done.
I prefer the first and last.
However the second one is very nice and may fit somebodys color scheme:>)))