P and S velocities, P delay and shear wave splitting calculated for three separate microstructural models shown at the top of the figure. Each model has the same modal fraction of muscovite (0.2), and the same muscovite (α= 0°) and quartz orientations (c-axis//y₂), but a different distribution of muscovite grains. Results for the AEH-FE method are microstructure dependent, and therefore colour-coded for each of the models. Results for the Voigt and Reuss bounds, and geometric and arithmetic means, are not microstructure dependent and therefore identical for each model.