Cracks in glass

I want to make the rainbow cracks that are in the crystal on the picture below.
The crystal is not hard to make. The cracks is harder. I tried with Cell Fracture and Cell Fracture Crack It but the cracks is too…controled and even or rather the blocks between the cracks are. Even if I use the random option.
And I do not know how to set the nodes and the light to get those pretty rainbows.
I apreciate any help I can get.