(a) The olivine hopper unit proposed by Faure et al. (2003a, b). (b) Olivine hoppers aggregate together to produce a dendritic structure with branches parallel to the hopper diagonals. (c) A schematic cross section parallel to (010) through the center of a euhedral sector-zoned Cpx crystal, after Welsch et al. (2016). The crystal aspect ratio a: c is 1.08: 1. The diagonals of the parallelogram represent the traces of the sector boundary between (001) and {−111} in the (010) plane. The orientations of the {001}^* and < 10–1 > directions are also indicated.