Manufactured Feldspar-quartz Sand for Glass Industry from Gneiss Quarry Rock Fines Using Dry Rare-earth Magnetic Separation

Abstract

ABSTRACT Feldspar concentrates, which have important applications in industry, have been mostly produced from pegmatites, granites, and sands from rivers. The metropolitan area of Rio de Janeiro contains major deposits of gneiss rocks which are the basis of crushed aggregate production. These rocks not only contain large amounts of feldspars, but also of mafic minerals. The paper demonstrates the use of rare-earth magnetic separation (REMS) in dry processing of a manufactured fine aggregate from a gneiss quarry. By removing iron-rich components from the low-value fine aggregate, a higher-added value feldspar-quartz concentrate for application in glass industry is produced. It is demonstrated that three-stage separation was successful in reaching the product specifications for use as fluxing agent and stabilizer in amber glass production. In order to demonstrate the robustness of the separation strategy, three different rock types present in the quarry were processed and results demonstrated that REMS is able to reach the manufacturer specification regarding iron content (<0.3% Fe2O3 in the product) in spite of the variation in feed composition. An industrial flowsheet on how this technology can be deployed in a plant producing quarry rock is proposed.