HIGH-SILICA ROCKS OF CENTRAL KARELIA - A POTENTIAL SOURCE OF QUARTZ RAW MATERIAL
The results of mineralogical-technological study of high-silica rocks of Central Karelia are discussed with a view to assessing the potential of using these rocks as natural material for producing quartz concentrates for various applications. Weakly transparent vein quartz, pebble quartz from Paleoproterozoic conglomerates and volcanogene-sedimen-tary silicites were subjected to optical and electron microscopy, microprobe analysis, X-ray fluorescence and diffraction analysis, atomic emission spectrometry. Technological studies of the silicites showed they can be enriched to produce quartz-feldspatic concentrate meeting the requirements to feedstock for fine ceramics (Fe<sub>2</sub>O<sub>3</sub> ≤ 0.2 %, K<sub>2</sub>O+Na<sub>2</sub>O ≥ 8 %, K<sub>2</sub>O/Na<sub>2</sub>O = 2). Owing to low Li, B and P content, quartz concentrates made from pebble quartz conglomerates fulfill the requirements for raw material for highgrade ferrosilicon production. Processing experiments were carried out, showing that the quartz concentrate of the -0.315 + 0.1 mm fraction obtained from weakly transparent vein quarts, with 34.6 ppm total impurity content meets the requirements for high purity quartz products of some grades (TU 5726-002-11496665-97) and is suited for extra pure fused glass utilizable in the manufacturing of semiconductor materials, electronics, lighting engineering, means of fiber-optic communication.