Effective Gold Recovery from Near-Surface Oxide Zone Using Reductive Microwave Roasting and Magnetic Separation

Abstract

High content of gold in near-surface oxide zones above the gold ore deposit could be recovered using cyanidation. However, restricting the use of cyanide in mines has made it difficult to recover gold within the oxide zone. In this study, we investigated an application of the reductive microwave roasting and magnetic separation (RMR-MS) process for the effective gold recovery from ores in a near-surface oxide zone. Ore samples obtained from the near-surface oxide zone in Moisan Gold Mine (Haenam, South Korea) were used in RMR-MS tests for the recovery of iron and gold. The effect of the RMR process on the recovery of iron and gold was evaluated by given various conditions of the microwave irradiation as well as the dosages of reductant and additive. The microwave roasting resulted in a chemical reduction of non-magnetic iron oxide minerals (hematite) to magnetite minerals, such as magnetite and maghemite. This mineral phase change could induce the effective separation of iron minerals from the gangue minerals by magnetic separation process. The increased iron recovery was directly proportional to the gold recovery due to the coexistence of gold with iron minerals. The RMR-MS process could be a promising method for gold recovery from the ores in near-surface oxide zones.

Characterization and identification of Au pathfinder minerals from an artisanal mine site using X-ray diffraction

“…Other sources of Au found are alluvial placer Au in the Offin river deposits in gravels as well as some mineralized placer Au reconstituted with minerals, such as Fe 3 O 4 and Fe 2 O 3 in quartz-pebble conglomerates of the Tarkwaian deposits [22]. Extremely oxidized, weathered or putrefied rock commonly located at the upper and exposed part of the ore deposit or mineralized vein known as ''gossan'' or iron cap serves as a guide to trace buried Au ore deposits in this area [23]. The surface oxides of the minerals at this site are usually red, orange to yellowish-brown color serving as an alteration to the parent rock or soil.…”

Elucidating Pathfinding Elements from the Kubi Gold Mine in Ghana

“…The Au in this soil is due to weathering activities and in association with the sulfide group of minerals and Fe-oxides. The smaller Au grains found a few meters from the surface occur beyond the stone line lateritic zone through chemical dissolution [51]. Thus, beyond the stone line, Au mineralization occurs with much coarser Au grains as a result of pedoturbation (soil horizon mixing) that goes downward due to the migration of fragments from the stone line, through the transition zone and to the saprolite, and vice versa.…”

Evaluación de metales preciosos (Au y Ag) en zonas de oxidación al noroeste de Artemisa (Cuba)

“…La historia de la minería del oro en Cuba ha sido descrita en numerosos trabajos publicados, sin embargo, no ha sido sistematizada acorde a las diferentes etapas del desarrollo socio -económico de la Isla. La producción de oro y su investigación han tenido un gran desarrollo en los últimos años en los cortes de meteorización lateríticos en el mundo, debido a la capacidad técnica del beneficio minero de menas de bajos contenidos y grano fino, así como a la experiencia acumulada en la explotación de los depósitos de tipo gossan, por el método de lixiviación en pila, asociados a yacimientos sulfurosos (Amorós et al, 1981;Freyssinet e Itard, 1997;Díaz-Martínez, 2010;Andreu et al, 2015;Yesares et al, 2015;Pérez-Vázquez et al, 2017;Kim et al, 2018;Kalinin et al, 2018;Ozdemir y Sahinoglu, 2018).…”