Michigan Lightning Stones

I probably found these lightning stones (septarian) at Pilgram Haven Natural Area in southwest Michigan.   The first pic is one as picked up off the beach.  The second one is a cab I made recently.   The white stuff filling the cracks/veins is calcite.  I think when you pick one up off the beach, the top lawer of the calcite is roughed up and it has a very white color and jumps out at you.   When you polish the calcite, it typically ends up very clear, almost to the point that the veins don't show up well against the host rock.   So typically, I don't polish many of these.   For some reason I thought this one might look good.   It has a lighter colored interior with veins radiating away from it.  In this case the veins at least showed up (aren't completely clear).   Maybe because the calcite is cracked below the polished surface?   

Does anyone know if there is a way to polish these so the calcite stands out better against the background?   

Thanks
Chris