During the recent moths I worked on a realistic looking procedural crystal shader and I think I finally managed to get something convincing.
You can download the whole node setup packed in a handy group here on blender swap.
Or for those only curious about the node setup you can find it here on imgur.
Here is an example of a render I did using this shader:
The .blend file is quite self explanatory, if you want to further customize the shader you will need to open the group and change stuff directly in there.
In that regard the most important setting the shader input lacks is the control over the color of the SSS.
In order to do it you will have to open the group, go to the frame named SSS and change the colors directly in the color ramp.
The shader is far from perfect and I’m still working on it, any suggestion or help is appreciated.