The impurity-striations and the dislocation loop series produced from the volume indentation by these impurity-striations in the float-zone grown silicon single crystals have been studied by means of chemical etching method. The experimental results have shown that the impurity-striations are oriented in the direction (110) of planes 111 in silicon, the length of the impurity-strialions is about 5-230μm, the dimensions on cross-section are about 2-3 pun. The geometrical structure of the dislocation loop series produced by volume indentation of the impurity-striation has been studied. The form and size of a single dislocation loop depend on the form and size of the impurity-striation. The dislocation networks resulting from the cross-superposition of the dislocation loop series and reactions between these dislocation loops have been observed and analyzed.