Utilisation of sillimanite minerals, their geology, and potential occurrences in Norway - an overview

Sillimanite, andalusite and kyanite constituted 2%, 74% and 24%, respectively, of the total western world’s production of sillimanite minerals in 1998 of a total of about 401 000 tonnes, of which about 95% was consumed by the refractory industry. The sillimanite minerals are mined mainly in South Africa (62%; andalusite), USA (23%; kyanite) and France (11%; andalusite), whereas the major consumers are found in the major iron- and steelproducing areas of the world. Production has declined over the last decade, due mainly to cutbacks in iron and steel production. Most economic deposits of sillimanite minerals can be classified as metamorphogenic and include contact-metamorphic andalusite deposits, stratabound podiform deposits of massive (corundum)-sillimanite and (corundum)-kyanite rocks and stratiform deposits of kyanite quartzites. The former occur within metapelitic sequences in the contact aureoles of plutonic massifs, whereas the two latter in most cases are interpreted as representing metamorphosed high-alumina sediments, derived from hydrothermal alteration centres in subaerial felsic to intermediate volcanites. All of these deposit types have also been recognised in Norway. The most promising occurrences are the andalusite schists within the contact aureoles of the Fongen-Hyllingen and Oyungen Gabbro Complexes in the Caledonides of Central Norway.