Gray boulders with sandpaper feel are graywacke sandstone with black layers of shale and white streaks of quartz veins. A prominent boulder south of the stream mouth has shiny slick surfaces with grooves, evidence that a fault moved, polishing and scraping the soft sandstone surface. Sandstone formed as turbidity currents of sand and mud that flowed rapidly down the continental slope to form layers in an oceanic trench. Alternating layers of black mud and gray sand result from the heavy sand sinking first followed by the lighter clay minerals in the mud. Smooth brown rocks are also sandstone, with more quartz in them so giving a lighter color.
Blocks made of pebbles are conglomerate, formed from stream gravels.
Light green rocks with black surfaces and green to white veins are peridotite . These are a message from the mantle. Shiney bronze pyroxene crystals are cut by green veins of serpentine. One block of peridotite has white fibrous veins of asbestos in it. In some outcrops, the peridotite has weathered orange, from oxidation of iron.