En echelon veins

Two parallel sets of en echelon veins in sandstone. Rock hammer for scale. Taken near Lehigh Gap, PA.

In structural geology, en échelon veins or "en échelon gash fractures" are structures within rock caused by noncoaxial shear.^[1] They appear as sets of short, parallel, lenses on the surface of a rock. They are planar structures within the rock. They originate as tension fractures and are subsequently filled by precipitation of a mineral, typically quartz or calcite.

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