A method of revealing screw component dislocations involving low‐energy cathodic sputtering with argon ions is presented. It is observed that hillocks having the shape of truncated cones with a spiral pattern on their tops form at the sites of intersection of screw dislocations with the surface. The hillocks probably form by mobile surface atoms attaching themselves to the step provided at the intersection of a screw dislocation with the surface. It is shown that the density of screw dislocations on a given plane depends on the orientation of the plane with respect to the crystal growth axis.