(a) Schematic of large-scale structure and relation between macroscale L and microscale ℓ. (b) Photomicrograph of a quartz-muscovite schist in cross-polarized light. The grey grains are quartz and the bright coloured grains are muscovite grains. (c) Representative synthetic quartz-muscovite microstructure. γ is the incidence angle, e^S_i and e^C_i indicate the reference orientations for the sample and crystal respectively. The macroscale is analysed using x-coordinates and the microscale is analysed using y-coordinates.