Mineralogy of Ten British Brick Clays

A B S T RA C T: Ten raw materials, typical of those used by the majority of British manufacturers of structural clayware, are shown to cover a wide range of mineralogical composition. Kaolin, mica minerals and quartz are always present, hough their relative percentages vary widely. Other minerals which may be present in more than trace amounts, are montmorillonite, dolomite, calcite, sepiolite and chlorite. The cor-relation between the mineralogy of a raw material and its physical characteristics is reasonably good; the presence of montmorillonite, in particular, can have a marked effect. The importance, however, of the degree of compaction of the raw material (largely a function of geologi-cal age) is emphasized. Variations in clay mineralogy appear to affect firing behaviour less than variations in the content of alkaline earths, where present.