Abstract
IN the course of an investigation into the surface structure of a wide range of mineral crystals, the results of which were reported to the Mineralogical Society in March 1951, a number of screw dislocations Were observed on the cube faces of one crystal of pyrite, FeS2. Fig. 1 shows a single screw dislocation ; while Fig. 2 exhibits a pair of screw dislocations of opposite sense, which ultimately form an almost closed step-line. The crystal was photographed using a metallurgical microscope, with bright-field illumination, and the surfaces were not silvered. Under these conditions, the very high visibility of the steps forming the main spiral patterns indicates that the layers are multimolecular. This point is further substantiated by the presence of some much thinner layers between the main steps. Examples of screw dislocations with a Burgers vector greater than unity, often considerably greater, have already been reported for cadmium iodide1, silicon carbide2, and muscovite3.
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References
Forty, A. J., Phil. Mag., 42, 670 (1951).
Verma, A. R., Nature, 168, 430 (1951).
Amelinckx, S., Nature, 169, 580 (1952).
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SEAGER, A. Screw Dislocations in Pyrite. Nature 170, 425 (1952). https://doi.org/10.1038/170425b0
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DOI: https://doi.org/10.1038/170425b0
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