Geological, petrographical and chemical aspects of economical use of foliated quartzites from São Thomé das Letras, Minas Gerais.

Abstract

São Thomé das Letras region is the biggest Brazilian center of foliated quartzites mining, with a present annual production of about 250,000 ton. The low rate mining recovery, estimated as less than 20% of total mining, is responsible for the 1,250,000 tons per year of undesirable wastes, as big piles inadequately disposed on the local environment. Looking for the best adjustment environmental mining, the Minas Gerais Environment State Foundation (FEAM), began in, since 1993, a inspection and orientation of the quartzites mining activities in São Thomé das Letras region. From 1996, this work was increased through the Minas Environment - Pedra São Tomé Mining Project, which, under the FEAM co-ordination, started studies of controlled disposal and economical exploration of wastes, vegetal planting of piles and less impacts mining techniques. In this context, geological, petrographical and chemical studies now done, lead to contribute with the mining activities, so as to the industrial use of the mining wastes and to the processing of São Tomé foliated quartzites. Some works improved by Minas Environment Project and, recently, by the Vale do Rio Verde University, from Três Corações city, demonstrated the technical viability of the use of quartzites in pressed and autoclaved bricks production. Some quartzite varieties are also been explored in glazed and enamel ceramics, with higher economical and technical advantages when compared with raw materials coming from alluvial sediments. It has been also studied other uses of grounded quartzites as mineral filling, filtrating material and general mortars which enable to foresee, at a medium time, a increasing uses of São Tomé quartzites. Keywords: dimension stones; covering stones; foliated quartzite; waste recovery; São Tomé quartzite.