This was a personal material challenge. My task was to make 100%... all of the material... procedural. No image textures, no painting, no nothing more than the internal nodes in Blender.
I think I succeeded!!
The material is in part published and all will be published soon. It's all for free.... but please, please... would be so grateful if you would like to be a Patreon of mine. It takes hours to do one material and I give it away :).
Anyway... all material you can download is here: http://www.blenderinsight.com/material-for-blender-2-8x-cycles/