ABSTRACT
Materials as diverse as glass and painted plaster are grouped together in this chapter; they are basically inorganic compounds derived from the minerals of the earth’s crust. Since silica forms 28 per cent of this crust a high proportion of silica is found in these materials. Artefacts can be made simply by shaping the raw materials or more elaborately with the use of heat or chemical reactions. Even after such treatment the materials are chemically and physically similar to the naturally occurring minerals, and so weather and decay as these do.
