Here is what I've finally gotten back on my study. Combining the lateral/vertical noise based on the altitude in texture, and my voronoi cracks setup, and a few PFs for variations.
File is a bit of a mess and I'm hoping to reduce functions down a bit, or figure out why it hung so long during rendering.
No where near perfect, and as you can tell from the left-hand side, you can't get too close without the surface noise getting soft.