Abstract
In a study of sandstones from the Coal Measures (Westphalian A and B) of the East Midlands, UK, fibrous illites exhibiting random core and lath structures were observed during SEM examination of material dried in air, but not during TEM examination of ultrathin sections made from the same material. Previous studies have reported random core and lath structures during TEM examination of extracted clay material and it is suggested that they are an artefact of the specimen preparation technique.