In the 2-dimensional model, grains are defined by nodes that are linked by straight boundary segments. An initial horizontal surface fracture is created with a user-defined roughness. All grain surfaces that are then exposed to the open fracture grow outward by repeatedly moving the boundary segments over small distances one at a time. The growth rate is fastest in the directions parallel and perpendicular to the c-axis. The habit of this mineral is that of a square.
Growth is fastest parallel to the c-axis and slowest normal to it.
Each crack-event, the lower wall rock is moved, in this case down and to the right. Exposed surface segments of grains grow into the crack. The crystallographic control on growth rate leads to the development of faceted grain surfaces. However, if the crack is too thin, such facets may never fully develop before the crack is sealed again. In this example faceting is just forming before sealing.