Applicability of Gravity Separation Method on The Ashashire Gold Ore Deposit from Benishangul Gumuz Region, Ethiopia
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Date
2023-06
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Addis Ababa University
Abstract
The current Project of applicability of gravity separation method for gold ore deposit was conducted in Ashashire locality of Benishangul gumuz region, North western Ethiopia. The purpose of this project is beneficiating the Ashashire gold ore deposit by applying the gravity separation. The Ashashire composites were produced to provide sufficient mass for this study and experiment includes sample preparation, head assay analysis of gold and multi-element, gravity concentration and mineralogical analysis. The study conducted to determine the applicability of gravity separation method by using KC on the Ashashire gold ore deposit. The samples were moderately ground to the standard grind size of P80 - passing 106, 75, 53 μm and this nominal size was selected for the preliminary assessment for Concentration optimization. During the study, a grind optimization was conducted on the composites sample with varying grind size to evaluate the effect of grind size on gold recovery. The gravity testing comprised three-stage concentration by centrifugal knelson concentrator to produce gravity concentrate. High recovery of gold from the gravity concentrates was achieved from the second gravity concentration. Based on the results from laboratory experiments, a grind size of P80 75 μm is selected as optimal size for the ashashire deposit using KC gravity methods. Increasing the grind size from P80 of 75 μm to106 μm decrease recovery rate from 75 % to 54 % or decreasing the grind size from P80 of 75 to 53 μm decrease gold recovery rate to 37%. It was observed that repeat gold head assays varied, indicating the presence of coarse gold particles and uneven gold particle distribution. The native gold grain in the ores is mostly associated with quartz and Fine gold is closely associated with pyrite, forming inclusions and dispersed within pyrite. According to the fire assay, chemical, and mineralogical analyzes data, only gold and telluride is commercially valuable component in the ores. Presence of 2.13 ppm Te was detected in the composite sample during head assay analysis. The differences between assayed head grades and calculated head grades would indicate that the gold is not evenly distributed within the ore and occurs as localised spots. Gold was identified to occur predominantly in the native form and as Au-Te. The sample subjected to gravity separation assayed about 2.6 g/t Au.
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Keywords
Ore, Gangue, Ashashire, Gravity, Gold, Telluride, Concentration, Knelson concentrator