the crystal of quartz is a hexagonal prism. The statement is quite true in so far as an ideal crystal is envisaged. But in nature one finds no two crystals exactly alike, although all are unmistakably hexagonal.
Von Franz uses the quartz crystal as a paradigmatic case to argue that natural, individual actuality exceeds the ideal type, thereby grounding the Chinese and Jungian preference for concrete, synchronistic reality over abstract causal law.
, Psyche and Matter, 2014thesis