Physicochemical and radioactive study of Colombontatalite ore from the Kisengo quarry in the DRC

This research concerns the assessment of radioactivity and the physicochemical characterization of columbotantalite ore extracted from the Kisengo quarry, located in the Tanganyika province of the Democratic Republic of Congo. The sample was taken from the Kisengo open-pit mine in Nyunzu territory located about 170 km from the town of Kalemie in Tanganyika province/DRC. It contained about 32% niobium, 21% tantalum, 6% iron, 7% manganese, 7% tin, 4% silicon and about 3% titanium and was analyzed by XRF. The results of the radioactivity tests revealed that the average dose rate, measured in nGy/h, was 329.72, or 0.038 mSv with the Identifinder device. This sample does not pose a risk of radioactive exposure, as the dose levels are very low, in accordance with the WHO range of 20 mSv and DRC Law 017/2002. Analysis of optical microscopy images of Kisengo coltan reveals the presence of a siliceous gangue (quartz) associated with pyroxenes as well as columbotantalite, which is the mineral of tantalum and niobium. Also present are cassiterite, a tin mineral (SnO2), and pyrolusite, a manganese mineral (MnO2). Granulochemical characterization revealed that tantalum and niobium are concentrated in the 500 micrometer fraction. The loss on ignition test indicated that niobium is the most abundant element in the analyzed sample, representing 31.97%, followed by tantalum at 20.75%. Finally, silicon and titanium are present and removed at 4.18% and 17.716%, respectively.