"SCHISTOSE" ROCKS AS A RESOURCE

Until the beginning of the 20th century, schist was a common building material in the Northeast and Centre regions of Portugal, due to the abundance of schist outcrops in these regions. The area of study is the NE Portugal characterized by the occurrence of abundant schist of different types and also of greenish basic rocks both having the ability to split according to more or less defined planes. Currently, the development of a RD 2- Carrying out a technological characterisation of the rocks and a systematic evaluation of the occurrences with good potential; 3- Promoting schistose rocks as a geological resource in areas from Northern Portugal. A first phase consisted on the selection of sites showing favourable geological and macroscopical characteristics enabling industrial exploitation. In the selected sites a detailed geological cartography accompanied by sampling of the most representative rock types for laboratorial studies was done. Petrography, chemical composition and physical-mechanical characterisation (compressive strength, flexural strength, apparent density, water absorption, abrasion resistance and impact resistance) were performed. In a second phase, the evaluation of the volume of rock with good characteristics for each potential application, within some of the selected areas, will be performed by geophysical methods using a vast number of short seismic refraction profiles in a predetermined regular grid. In this contribution, we present as a “Case study” the “Tanha quarry” where a lithology of “Complexo Xisto-Grauvaquico” affected by thermal metamorphism is exploited as industrial stone, but where a preserved area for ornamental stone exists.