Field evaluation of fine-grained industrial minerals

摘要

Evaluation of exploration targets for potential industrial minerals can sometimes be complex as many minerals share a similar appearance and geological association. Examples include sepiolite, kaolin, pyrophyllite, zeolite and even bentonite. All can occur as pale-coloured, fine-grained alteration products within siliceous volcaniclastic sequences. This paper describes some simple physical and chemical tests useful in field evaluation. The tests rely on the determination of key characteristic or 'index' properties. The results can be used in 'screening programmes' to assist identification of high-quality material in the field, and to reduce the volume of laboratory analysis required by eliminating material of poorer quality. Examples are: the relative proportions of dolomite in carbonate rocks measured using the non-toxic heavy liquid, sodium polytungstate; systematic section logging and observation of physical properties such as colour, bulk density, particle-size and the presence of clay and iron staining in assessing the quality of diatomite; and the purity of natural zeolites determined through the use of a field test that exploits their reversible hydration characteristics.