Abstract:

Refractory gold ores resources is widely distributed in the Gansu Province，Qinghai Province and Guizhou Province of China.There is usually a high gold content in these refractory gold ores，but the refractory gold ore contains generally a certain amount of Sb-bearing，As-bearing and C-bearing minerals，which is the important factor effecting the recovery of gold from the refractory gold ores.In recent years，more attention was paid to how to improve the recovery of gold from the refractory.During the development and utilization of the refractory gold ore，the research of mineralogy plays an important role in investigating the occurrence state of gold in ores and the factor effecting the recovery of gold. In addition，mineralogy is still a key parameter to determine the reasonable processing technology. In this paper，the mineralogy of a refractory gold ore from Qinghai Province of China was investigated，which contains Au 5.2×10^-6，S 1.82%，As 1.01%，Sb 0.73% and Fe 4.19% respectively. The recovery of gold by the cyanide leaching is less than 50% in laboratory scale.To find the reason for the low recovery of gold by cyanide leaching and the occurrence state of gold and Au-bearing in ores，the processing mineralogy of the refractory ore was investigated by a method combining the X-ray diffraction（XRD） and scanning electron microscope（SEM-EDS） with the optical microscope.Results from the processing mineralogy indicat that there are three occurrence state of gold in this refractory ore，there are the natural gold，the gold enclosed in sulfide minerals and the gold enclosed in gangue minerals.The natural gold with the percentage of 42.87% in total gold is mainly distributed in the interface between stibnite，arsenopyrite and quartz，and the natural gold is easily recovered due to the coarse dissemination particle size.The gold enclosed in sulfide minerals is 46.83% with Au content of 2.43×10^-6.In this refractory gold ore，most of gold was enclosed in sulfide minerals such as stibnite，arsenopyrite and pyrite in the formation of microscopic or submicroscopic gold，which is difficult to recovery by cyanide leaching due to the fine dissemination particle size.The gold enclosed in sulfide mineral cannot contact with the leaching reagents，which is the primary reason for the low recovery of gold with the cyanide leaching.In addition，a part of gold in ores with the percentage of 10.3% is distributed in gangue minerals such as quartz，feldspar and calcite in the formation of micro-inclusion.Basis on the study of the occurrence state of gold and the characteristics of the intercalation relationship of the main gold-bearing minerals，the main mineralogical factors affecting the recovery of gold in the ore were discussed.In view of the low proportion of natural gold in the refractory gold ore and the high content of gold encapsulated in sulfide minerals，the reasonable beneficiation process of “rough grinding-centrifugal gravity separation-fine grinding-flotation-floating tail cyanide leaching” was proposed to strengthen the recovery of coarse-grained natural gold and sulfide mineral-coated gold in the ore.Laboratory studies have shown that this process can achieve high-efficiency recovery of gold in the refractory gold mine.The results provide an important reference with the comprehensive utilization of the refractory gold ores.

Key words: refractory gold ore, Sb-bearing gold ore, occurrence state, embedded characteristics, processing mineralogy