Field evaluation of fine-grained industrial minerals

Evaluation of exploration targets for potential industrial minerals can sometimes be complex as many minerals share similar appearance and geological association. Examples include sepiolite, kaolin, pyrophyllite, zeolite and even bentonite which can all occur as pale-coloured, fine-grained alteration products within siliceous volcaniclastic sequences. This paper describes some simple physical and chemical test methods useful in field evaluation of certain industrial minerals. Such test methods rely on the determination of key characteristic or ‘index’ properties. They can be incorporated into ‘screening programmes’ to assist identification of high quality material in the field, to reduce the volume of laboratory analysis required by eliminating material of poorer quality. The methodologies are illustrated with examples from industrial mineral evaluation studies carried out by the British Geological Survey (BGS), including density testing to discriminate limestone from dolomite, classification of diatomite using physical property testing and identification of zeolite-rich rocks using a field test based on the rehydration of zeolite.