A Texture-Pack I made for CG_Trader. I use Agisofts Photoscan, Gimp, Krita and Blender. All work is done on Linux.
The source pictures are from the Himalayan mountains.
The rendering is done in Blender via Cycles. The material setup-up is nothing special.
If you are interested in the Texture-pack: https://www.cgtrader.com/3d-models/scanned/various/scanned-rock-texture-pack-pbr-ready
Or if you want a really big Texture-pack, containing various textures: https://www.cgtrader.com/3d-models/scanned/various/mega-scan-texture-pack