Process Mineralogy and Beneficiation Methods for Manganese Ore

The process mineralogical characteristics of manganese ore form the fundamental basis for devising pre-concentration and slag removal schemes. Unlike sulphide ores such as copper and gold, manganese ore typically exhibits characteristics such as multi-mineral association, uneven grain size distribution and a tendency to become muddy. The feasibility and efficiency of pre-concentration and tailings disposal technologies depend directly on the degree of difference between manganese minerals and gangue minerals in terms of macroscopic and microscopic physical properties, such as density, magnetic properties, electrical conductivity and atomic density.

Given the significant density difference between manganese oxide minerals and the main gangue minerals, gravity separation has consistently been the core process for pre-concentration and gangue removal in manganese ore. Among these, heavy-medium separation and jigging are the most widely applied in industrial practice due to their high throughput and technical maturity.

Heavy-medium separation

Heavy-medium separation (DMS) is widely recognised as the gravity separation technology currently offering the highest separation accuracy; it is suitable for processing difficult-to-process manganese ores with a high content of near-density materials. Its core principle lies in the use of a high-density suspension as the separation medium. During the separation process, manganese ore particles with a density greater than that of the suspension sink, whilst gangue particles with a density lower than that of the suspension float, thereby achieving precise stratification and separation of materials according to density.

Jigging

Jigging utilises a vertically alternating medium flow (water or air) to cause the mineral particle population to re-stratify within the bed according to density. Compared to DMS, although the jigging process offers relatively lower separation accuracy for near-density materials, it still holds an important position in the processing of low-grade ores due to its compact equipment design, the absence of the need for expensive heavy media, and its excellent resistance to slime interference. The jigging process follows the principle of ‘stratification by density’ and is primarily governed by disruptive settling and suction effects caused by changes in the looseness of the bed. During the rising phase of the water flow, the bed is lifted and loosened, with heavy minerals (manganese) rising more slowly than light minerals (silica); during the falling water phase, the bed compacts, and fine-grained heavy minerals pass through the gaps between coarse particles (i.e. ‘screen penetration’), entering the lower part of the trough to form the concentrate. This demonstrates that jigging is not only suitable for recovering coarse-grained manganese ore but is also effective for certain high-density fine-grained manganese ores; the key lies in the suction effect during the falling water phase, which promotes the migration of fine-grained heavy minerals.

Magnetic Pre-concentration Technology

Given the paramagnetic nature of manganese minerals, magnetic separation is an effective alternative to gravity separation for processing fine-grained ores or those with negligible density differences. For manganese ores with fine-grained ores or those that have become muddied, traditional gravity separation often yields low recovery rates, whereas magnetic separation can effectively recover ultrafine manganese minerals. In the field of pre-concentration and waste disposal, dry high-intensity magnetic separation has attracted considerable attention due to its lack of need for dewatering and its short process flow. With the development of high-field-strength, high-gradient magnetic separation equipment (such as vertical-ring pulsating high-gradient magnetic separators), magnetic pre-concentration has evolved from a simple ‘enrichment’ function to a pre-concentration and waste-rejection function characterised by ‘substantial waste rejection, energy saving and reduced consumption’; this has become a key technological trend in the processing of low-grade, fine-grained and complex manganese ore resources.

Intelligent Optoelectronic Sorting Technology

Surface optical sorting is one of the earliest sensor-based sorting technologies to be commercialised in the mining sector. This technology primarily relies on high-frequency line-scan cameras (CCD or CMOS sensors) to capture optical characteristics such as colour, texture and lustre on the surface of ore, using image processing algorithms to identify differences between materials. In manganese ore beneficiation, this technology is widely used to separate black manganese oxide ore from gangue minerals with significantly different colours, such as white calcite and pink feldspar, thereby achieving pre-rejection of waste and grade enhancement.

XRT is currently the most widely applied and effective dry waste rejection process. It utilises dual-energy X-rays to penetrate the ore; the identification process is unaffected by dust, moisture or oxide films on the ore surface, and can directly detect the internal structure of the ore, effectively processing lump ore in the -75 mm +6 mm particle size range. Compared with traditional manual sorting and photoelectric colour sorting, XRT can accurately identify ore that is coated with manganese ore on the outside but is actually waste rock on the inside, significantly improving sorting accuracy.