青海某难浸金矿的工艺矿物学研究

Study on the Processing Mineralogy of a Refractory Gold Ores from Qinghai Province

青海某金矿石中含金5.2×10^(-6),硫1.82%,砷1.01%,锑0.73%,铁4.19%,实验室直接氰化浸出时金回收率不足50%,属于典型的含砷锑难浸金矿。为查明影响金浸出的矿物学因素,采用X射线衍射仪(XRD)和扫描电镜(SEM-EDS),并结合传统的光学显微镜对该难浸金矿中金的赋存状态及主要载金矿物的嵌布特征进行了研究。结果表明:该矿石中金的赋存状态主要有3种,即可见自然金(明金)、硫化矿物包裹金和脉石矿物包裹金。其中,可见自然金占比较低,仅为42.87%,主要嵌布在辉锑矿、毒砂和石英等矿物颗粒间或裂隙中;硫化矿物包裹金占比为46.83%,主要以显微、次显微金或固溶体的形式赋存于毒砂、辉锑矿和黄铁矿等硫化矿物中;脉石矿物包裹金占比为10.3%,主要以显微、次显微金或微细粒包裹体的形式赋存于石英、长石和方解石等脉石矿物中或矿物颗粒间。由此可知,自然金占比低、硫化矿物包裹金和脉石矿物包裹金含量高是造成氰化浸出时金回收率低的主要原因,工艺矿物学研究结果为该金矿的合理开发利用提供了重要参考。

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.