The importance of being imperfect

Abstract

We imagine crystals as Platonic ideals of perfection, but real ones are always faulty and impure. Most could not even have formed without faults. The endless variety of crystalline nature, leading for example to mechanical strength, brittleness, plasticity, transparency, reflectivity, colour, electrical conductivity, transistor behaviour, phosphorescence and photographic sensitivity, is largely brought about by faults and impurities.