DIRECT OBSERVATION OF DISLOCATIONS AND PLASTICITY IN MINERAL CRYSTALS WITH SPECIAL REFERENCE TO PLAGIOCLASE.
AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS
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The AFCRL mineral study determines deformational behavior in important rock-forming minerals as a function of their internal and external environment. Internal perfection of crystals is being determined by chemical analysis, thermoluminescence, optics, X-ray studies and by use of etching and the electron microscope to study dislocation density and pattern. External environment is being determined by experimentally deforming crystals under known conditions of temperature, pressure, rate of strain and total strain. In this manner crystal deformation can be used to help interpret the previous history of these minerals either singularly or as mixtures in rocks. Previous studies involving the application of the etch-pit method to minerals and the influence of dislocations on plasticity are reviewed. In particular the relationship of dislocations to twin gliding and translation gliding is discussed, with special reference to plagioclase. Author