Brittle faulting refers to the faulting of solid rock (as opposed to molten and semi-molten rock). Evidence of brittle faulting includes slickensides, fault breccia and gouge. Slickensides are parallel striations rock surfaces produced by relative motion across opposite sides of fault, joint or fracture planes. As the broken rock layers move past one-another, their faces scrape/scratch/polish each other creating slickensides. A breccia is a rock that is made up of angular rock fragments. A fault breccia can form when rock along a fault is fractured due to the grinding motion of the two fault blocks and the broken fragments are cemented together by subsequent mineralization. Gouge is a layer of soft, earthy or clayey rock material along the wall of a vein, so named because a miner can "gouge" it out to facilitate the mining of the vein itself. Gouge can form when rock along a fault or fracture is pulverized due to the grinding motion of the two fault blocks.