Effects of compression direction on the plasticity and rheology of hydrolytically weakened synthetic quartz crystals at atmospheric pressure

A hydrothermally grown synthetic quartz crystal with 370 plus or minus 60 ppm hydroxyl impurity was cut into right rectangular prisms in eight crystallographic orientations. The prisms were compressed under constant axial force corresponding to a uniaxial stress of 140. 0 plus or minus 0. 5 MPa, and temperatures of 510 degree and 750 degree C. All but one of the samples sustained permanent axial strains of 2-3%. The operating slip systems were established from specimen shape change, slip bands, and dislocation etch pits on polished surfaces, crystallographic orientation changes, stress optical features in thin sections, and transmission electron microscopy.