Geological and mechanical investigation of the Såt extraction prospect for hard rock aggregates in Espevik, Rogaland
A new potential extraction area for hard rock aggregates around Såt, near the existing quarry in Espevik has been mapped geologically. The main focus has been geological mapping and interpretation combined with sampling of the different rock types for mechanical testing and microscopical analyses. The geology in Såt prospect is complex. The dominating rock type is porphyritic biotite gneiss-granite which occur in the north-eastern half of the prospect. The south-western half consists of fine-grained grey veined gneisses, which are intruded by tonalitic porphyritic to even-grained grey biotite gneiss-granitoids. The two rock types occur in roughly even proportions. The diffrent types of biotite gneiss-granites and gneiss-granitoids are generally well-foliated to sheared-mylonitic, which give a textural variation in addition to a compositional variation. The Los Angels values for the porphyritic biotite gneiss-granite are in average similar to those for the Espevik gneiss-granite. The rock types within the south-western half of the prospect, mainly fine-grained grey gneisses and grey biotite gneiss-granitoids, shows much better results for the Los Angels test. There are no significant differences in the polished stone value for the different rock types. The mechanical properties for the rock types within the Såt prospect area evaluated as interesting for the export market in Europe. Because of the variation in rock types and mechanical strength, it is proposed to carry out a mining operation with selective extraction of rocks. In this way, materials from the different rock types with different mechanical properties could be mixed to achieve products that meet the various quality and requirement demanda in the market.