Check-out my new product :

This pack contains 6 highly detailed procedural materials for Blender.

Each material has it's own customized node group, so you will be able to customize it with different values like scale, colors, wetness, displacement, AO (ambiant occlusion) :

How to import the materials :

• Go to File → Append

• Look for the file that contains the materials and double click on it

• Go to the material folder

• Select the material and click on "Append"

• Now you can assign the material to your object and customize it in the "material properties" panel or in the Shading workspace.