Stress birefringence microscopy of dislocations in type-Ia natural diamond

Abstract

The stress fields around dislocations and groups of dislocations in relatively perfect natural type-Ia diamonds have been imaged by polarization microscopy. In crystal slices parallel to the {111} growth faces, dislocations and bundles of dislocations with edge components generally parallel to ⟨110⟩ were observed end-on. In one crystal plate, intrinsic stacking faults parallel to {111} could also be recognized. A correlation between surface trigons and dislocation images was found. For {110} plates dislocations were observed side-on. Only edge components parallel to the microscope's optical axis were revealed. Contrast characteristic of edge components parallel to the crystal plate surface or of screw components was never observed. On as-grown octahedral surfaces the summits of shallow growth hillocks were found to correspond with dislocation bundle outcrops.