Study of technological properties of the sample ethiopian iron ore of the arabian-nubian shield. Part 2. Microscopic analysis of ore samples with a thickness of +40.0+5.0 mm

As a result of the research, the mineral composition of the mineralogical and petrological varieties of material of the 10-20 mm and 20-40 mm size classes of the studied ore sample was specified. Transparent and polished sections of the above-mentioned granulometric samples were prepared. Microscopic examination was carried out using a transmitted and reflected light microscope «Carl Zeiss Jena NU-2 Microscope». A description of the discovered minerals was completed. It was found that the main ore minerals of the studied ore are dispersed hematite and hydrohematite, and their amount is about 54.0% of the total volume. Microscopic analysis also revealed hydrohematite spherulites, including in the intergranular space in quartz aggregates. It is shown that secondary ore minerals in the studied raw materials are goethite and hydrogoethite. Microscopic analysis showed their content at the level of 4.0 %. The color of goethite and hydrogethite, which are represented by iron hydroxides of yellow, brown, brown and black color and their form in the form of nodular aggregates, spherulites of crusts, and nest-like aggregates, is also determined. It was found that the main non-metallic mineral in the studied raw material is quartz, the content of which is on average 30 %. This mineral in the sample of the studied ore is characterized by a variety of morphological features and a wide range of grain sizes – from several micrometers to several centimeters. Microscopic examination of quartz showed that it is represented by xenomorphic grains with a complex nature of fusions with other minerals, rounded and acute-angled grains, chalcedony (agat) grains and thin-prismatic crystals. The presence of a secondary non-ore mineral, which has clay properties and is represented by kaolinite, is also shown. An additional study was carried out, in which chalcopyrite – an additional component of iron ore raw materials – was analyzed. The conducted microscopic studies made it possible to draw a conclusion about the mineral and petrological characteristics of the raw material. It is shown that the type of iron ore of the Arabian-Nubian shield is similar to ores of volcanic-sedimentary origin and brown iron ores