Mineral beneficiation and ore dressing

Mineral beneficiation is the process of separating economically essential minerals from their respective ores. For example, aluminum is extracted from bauxite ore. Ores are the aggregates of rocks from which the desired minerals are extracted. They can either contain minerals or metals that are economically important to humans. If the quantity of metal or minerals in the ore is low, it is wasteful to spend so much machinery and labor to get the minimum result. Spalling was a common process in ancient times when there was the absence of machinery. In this process, the raw ore was broken up by hammers and wielded by hand. The main motive of ore dressing is to remove unwanted particles such as dust and other minerals, gangue or matrix from the ore. Microbes in Mineral Beneficiation helps in the better dissolving of certain minerals in the water. Therefore, microbes have a significant role in the beneficiation of minerals. Although the process seems quite simple and easy, there are several steps in ore dressing involving heavy machinery to get the final product.

Steps in Mineral Beneficiation

The ore dressing or mineral processing is complicated, with several steps depending upon the metal to be extracted. The typical stages of mineral beneficiation are as follows:

Communication 

Communication is made on dry material or slurries to reduce their size. Communication involves either the crushing or grinding of ores. The crushing process is by the run-of-mine, whereas the ground, i.e. the second step after crushing, is on dry material. Heavy forces such as compression, impact (mainly for crushing) and attrition (mainly for grinding) are responsible for crushing or grinding. Crushing and drying are slightly different, as crushing involves a drying process. On the other hand, grinding is a wet process.

Sizing 

After crushing and grinding, the next step is sizing these materials. As the name suggests, sizing is the process of the separation of particles based on their size. The equipment involved in sizing is Bar Screens, Wedge Fire Screens, Vibratory Screens, Flip Flop Screens etc. The sizing consists of two procedures, screening and classification. Screening involves introducing materials to the screen surface and allowing the finer particles to fall through the screen. The greater particles remain behind, and the smaller ones get out, just like flour sieving. 

The basic principle of classification is that particles with different sizes, but the same density will settle within a given fluid at different rates. Therefore, classification involves the separation of particles based on their settling velocities. 

Concentration 

Concentration is increasing the percentage of the desired mineral in a given ore. 

• Gravity Concentration: Gravity concentration is one of the oldest techniques (dates back to 3000 BC) that involves the separation of minerals with different gravity based on their relative movement in response towards the gravitational force. It may affect other forces such as centrifugal force, magnetic force, buoyant force etc. we must know the suitability of the gravitational concentration of specific ore before continuing with the process. 
• Magnetic Concentration: This process involves separation using a magnetic force. Any susceptible magnetic substance attracts the magnet (like in iron mining). These magnets can either be ferromagnetic, diamagnetic or paramagnetic. Ferromagnetic substances are already magnets, i.e., the natural magnets. The paramagnetic substances are weakly attracted towards the magnetic field, and diamagnetic substances strongly attract towards any magnetic field. For example, separating iron scraps from ores, we can hang a strong magnet that will attract the iron scraps. 
• Froth Flotation: In the froth flotation process, the desired minerals are separated by inducing them to accumulate over the froth layer. The froth flotation process involves the separation of hydrophobic minerals (minerals that repel water) from hydrophilic (attracts towards the water) gangue. 

Electrostatic Separation

This separation principle is that different particles with different electrostatic affinities absorb different amounts of current from the surrounding. Therefore, they deflect in different directions in the electric field. They are most beneficial in separating mineral sand. 

Benefits of Mineral Beneficiation

The benefits of mineral beneficiation or ore dressing are as follows:

• High volume production in lesser time.
• Increases the metal content of the ore.
• Decreases the gangue content to get the most out of the ore.
• It provides raw materials that support the country’s infrastructure and economy.

Conclusion 

Ores are the primary source of obtaining minerals by mineral beneficiation. The process involves several steps depending upon the ore and its composition and properties. Ores are the aggregates of rocks or minerals from which the desired minerals are extracted. They can either contain minerals or metals that are economically important to humans. Only the ores with a high percentage of minerals are beneficiated, as they will provide the best output. On the other hand, ores with a lesser concentration of minerals will give very little output. The benefits involve the high volume production in less time, Increasing the metal content of the ore, Decreasing the gangue content, getting the most out of the ore etc.