Technological investigations of alluvial garnet sands from the Kola Peninsula

Abstract

The paper presents the investigation results on two technological samples of alluvial garnet sands from Yavr area located in the southwest of the Kola Peninsula. The first sample TP-11/2 (mass 250 kg) was used to study the granulometric, mineralogical and chemical composition of garnet sands. The second sample TP-12 (mass about 6.5 ton) was used to manufacture some garnet concentrates for the waterjet cutting testing. It has been established that the main material of TP-11/2 sample is concentrated in the size of -0.63 + 0.10 mm. The larger particles make 5.0%, the smaller particles make 7.0%. The size distribution in the TP-12 sample is similar. The main minerals of the sands are quartz, feldspar, garnet, amphiboles, pyroxenes, mica, rutile and ilmenite. The percentage of secondary minerals represented by sillimanite, kyanite, apatite, tourmaline, graphite, magnetite, and single zircon grains is less than 2%. Garnet in Javr area sands is 9–-97% in the free phase. The mass concentration of garnet in the sands is 15–19%, the mass concentration of rutile is 1.0%. Garnet corresponds to almandine in composition. A small part of garnets (about 15–20%) contains a pyrope component. The prevailing shape of garnet grains is angular; the profile of the grains is predominantly isometric and elongated. The garnet sands were dressed at the pilot concentration plant of the Mining Institute, in the gravitymagnetic-electric circuit using the following equipment: a fine screen, a spiral sluice, a concentration table, a weak field magnetic separator, a high-intensity magnetic separator, an electrostatic separator for scavenging of rough garnet concentrates. According to the test results, all garnet concentrates with the size of –0.63 + 0.315 mm, –0.315 + 0.18 mm, –0.18 + 0.10 mm were assumed suitable for the waterjet cutting.