Dislocation microstructures have been characterized by transmission electron microscopy in polycrystalline coesite deformed experimentally at 4 GPa, 1200 °C. Burgers vectors have been determined by large-angle convergent-beam electron diffraction. Sample orientation was assisted by precession electron diffraction to overcome difficulties arising from pseudo-hexagonal symmetry. The results are explained by using a pseudo-hexagonal setting. We found that most dislocations observed are of the ⅓〈21̅1̅0〉 type. No clear glide plane was identified, suggesting that climb is activated under these conditions. This conclusion is supported by the observation of numerous subgrain boundaries. We have also observed some [0001] dislocations. Finally, the C12/c1 space group to which coesite belongs being centred, an additional slip system is observed: ⅙ [1̅21̅3] (011̅1) (½ [1̅10] (110) in the monoclinic setting).

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