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Gallery of Slickensides


Slickensides are naturally polished rock surfaces that occur when the rocks along a fault rub against each other, making their surfaces smoothed, lineated, and grooved. Their formation may involve simple friction, or if the fault surface was once deeply buried, actual growth of oriented mineral grains may respond to the forces on the fault. Slickensides appear to lie between the grinding of shallow rocks that makes fault gouge (and cataclasite) and the deep-seated friction that melts rock into pseudotachylites.

Slickensides may be scattered surfaces as small as your hand or, in rare cases, thousands of square meters in extent. The corrugations show the direction of motion along the fault. Unusual minerals may occur given the combinations of fluids and pressures along slickensides. But even familiar rocks, as we will see, take on unusual features too.

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The telltale glintSlickensides on a Hand SpecimenLook toward the sunSlickensides on an OutcropWe'll start smallSlickenside in LimestoneAn uncommon host rock for slickensidesSlickenside in Sandstone, Wright's Beach, California
Serpentine slips in peridotiteSlickenside in Peridotite, Klamath Mountains, CaliforniaPervasive slickensidesSlickensides in SerpentiniteOutcrop-scale slickensideSlickenside in Serpentinite OutcropA rare black flash Slickenside in Basalt
A dark mirrorCloseup of Basalt SlickensideDon't mistake these for striationsSlickenside in Metabasalt, Isle Royale, MichiganOverview of the outcropSlickenside in ChertRight in an urban neighborhoodCorona Heights Slickenside, Beaver Street
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