Gold Ore Deposits and Beneficiation Processes

Depending on the form in which gold minerals occur, the composition of associated minerals, and the difficulty of ore beneficiation, gold ores can be classified into various industrial types, such as placer gold, sulphide gold ores, gold-bearing polymetallic ores and carbonaceous gold ores.

Gravity separation, which relies on differences in mineral density to achieve separation, is the classic processing method for placer gold. As it requires no chemical additives throughout the process, it causes minimal pollution, utilises simple equipment, and has low operational, maintenance and energy costs, making it suitable for the large-scale processing of coarse and medium-grained gold ore. However, this process is ineffective at recovering fine-grained gold and has limited separation purity; consequently, it is not generally used as the main processing route. Commonly used equipment in the industry includes chutes, jigs, shaking tables and Nielsen centrifugal separators, which are often combined with other processes to specifically recover coarse-grained gold at an early stage, thereby reducing the load on subsequent processes.

Flotation is the core separation method for all types of sulphide gold ores. Most gold-bearing sulphide minerals possess excellent natural floatability; they can form stable froth within the slurry, entraining gold particles to achieve enrichment, thereby significantly simplifying subsequent smelting processes. Floatation equipment is divided into two main types: air-agitated and air-injected agitation. The choice of equipment directly affects processing efficiency and metal recovery rates.

Floatation reagents are key to regulating separation efficiency and are divided into three categories: collectors, depressants and activators. Collectors utilise an amphiphilic structure to alter the hydrophobicity of the mineral surface, enabling gold-bearing particles to adhere to bubbles and float to the surface; inhibitors modify the surface properties of gangue to prevent impurities from floating simultaneously, thereby enhancing concentrate purity; activators, meanwhile, activate surface sites on gold minerals to promote collector adsorption. The combined action of these three agents achieves efficient separation of valuable minerals from gangue. Both processes can be used independently or are often employed in combination to suit gold ore resources with different embedding characteristics.