'Industrial minerals' are those minerals or assemblages of minerals which are economically important because of their physical or chemical properties, rather than their metal or energy content. The term is synonymous with 'non-metallic minerals', and also includes rocks, although the full term 'industrial minerals and rocks' is often shortened. Industrial minerals are not normally processed by the user, and conse­quently are sold on the basis of their performance in specific end-uses. Most must be controlled to precise physical or chemical limits. They can be divided into nine classes, each with a differ­ent end-use: (1) structural minerals (2) pigments (3) process aids (4) ceramics and refractories (5) chemical source minerals (6) abrasives (7) foundry minerals (8) gemstones (9) electrical minerals. The main purpose of this manual is to shed a little light on the kinds of material tests that are required for evaluating an industrial mineral, because many geologists are unfamiliar with the procedures. The approach is rather different from that applied to metallic ores, where the main information required consists of a set of assay values for the major elements (plus penalty or bonus elements), data on grain size liberation characteristics, and the composition of ore and gangue minerals. The evaluation of non-metallic minerals, however, requires performing a series of tests which differ from mineral to mineral. Industrial minerals are valued mainly for their physical properties, hence most of the tests which are done are physical in nature. A full chemical analysis is important to carry out in minerals destined for the chemical industry, and also constitutes an essential check on purity. The development of an industrial mineral deposit may be influenced by many economic factors. The following are of particular significance: (1) the dominant importance of marketing. (2) the range and complexity of the mineral products required, what specialised processing is required, and the growing importance of suiting the material to consumer needs. (3) the transportation and distribution costs of commodities, many of which have a high bulk but a low value. (4) the ability to substitute one commodity wholly or partly for another. (5) the cost of reclamation of mined land where very large volumes of material have been removed by open cut mining methods. (6) the growing need for control of possible pollution caused by processing plants and in the use of the mineral. These factors are by no means mutually independent, and do not all apply to every industrial mineral. Nor are they unique to industrial minerals, but in their case are relatively more important than to metallic minerals and to fuels. The consumption of industrial minerals is more regular than that of metals because, apart from the structural minerals, most industrial minerals are consumed in making non-durable goods such as chemicals, paper, paint, or processing aids; the level of demand for these varies much less than that for goods in which metals are used.