Separation of Gold from Gold Bearing Minerals by Conventional and Microbial Processing Techniques

Abstract

Gold is one of the most important and valuable metal because it's unique physical and chemical properties. It is used in high-tech industries and medical applications. Gold occurs in nature as metal or as alloys with other metals. It is usually associated with quartz or pyrite minerals. It is a rare element with a concentration of 0.005 ppm of the earth's crust. The low-grade deposits contain 3 and 6 ppm, so it is a challenge to meet the commercial grade (3000-4000 ppm). There are more than one hundred gold deposits are known in the Eastern Desert of Egypt. On the mineralogical basis, three gold- bearing formations are distinguished as sulfide, ferruginous quartzite, and quartz vein formations. The latter is the only source of gold in Egypt. This study was carried out on a sample from the El-Hudi gold deposit. Wadi El-Hudi lies in Egypt’s Eastern Desert, East of Aswan. The gold-bearing mineral ore composed of a quartz mineral of about 96.5% SiO2. It contains 1.8% Fe2O3, 0.66% Al2O3, and 1% of other impurities with a trace of gold  12 g/t. Thus it must be upgrade to meet the commercial grade of 3000-4000 g/t. The gold grains ranged in their size from 10 to 40 µm. Sericite mineral is common in discrete gold-bearing veins. Pyrite is another main vein mineral that occured as fine to medium-grained. The crushing and grinding carried out to liberate the gold from its associating gangues. Three feeds prepared by grinding the whole sample to less than 0.8 mm, less than 0.2 mm, and less than 0.075 mm in order to reduce the grinding cost. Usually, the gold is upgraded using the gravity separation, flotation, cyanidation, or a combination of them. The gravity