although kaolin is a mineral little colour change occurs on rotation in this sample, probably due to the thinness of the particles but mainly because kaolin is only slightly birefringent. Note the different, mostly angular, shapes. Sample dispersed in water, the dispersion was diluted and smeared on microscope slide and left to dry before micrographs were taken. Sample courtesy Hugo Geerdinck, Coldenhoven papier, Eerbeek [micrographs and z-stacks BvV].