Leaching is a process widely used in extractive metallurgy where ore is treated with chemicals to convert the valuable metals within into soluble salts while the impurity remains insoluble. These can then be washed out and processed to give the pure metal; the materials left over are commonly known as tailings.

Once the ore has been mined it is usually crushed into smaller pieces that can be processed more easily. In modern times several new techniques are used to extract the mineral from the ore, in addition to smelting. The most common methods are flotation, leaching and use of redox reactions.

Unit operations. Mineral processing can involve four general types of unit operation: comminution – particle size reduction; sizing – separation of particle sizes by screening or classification; concentration by taking advantage of physical and surface chemical properties; and dewatering – solid/liquid separation.

Mineral processing

1. Separation and purification.
2. Materials processing.
3. Flotation.
4. Touchstone.
5. Beneficiation.
6. Fire-assay.
7. Process metallurgy.
8. Radiometric separation.

Ore dressing is a process of mechanically separating the grains of ore minerals from the gangue minerals. It is done in order to produce a concentrate containing most of the ore minerals and a tailing part (discard) containing the rest of the gangue minerals.

Grade: The percentage of a metal in a product. Grain: A discrete chunk of pure mineral. Gravity methods: In mineral processing, refers to a separation process whereby gravity is utilized to effect separation between particles of greatly different densities. Grinding: Size reduction primarily by attrition.

The first step in the production stage is recovering the minerals; this is the process of extracting the ore from rock using a variety of tools and machinery. The second step is processing; the recovered minerals are processed through huge crushers or mills to separate commercially valuable minerals from their ores.

Generally, mineral processing begins when an ore is delivered from a mine, to a processing facility. At this point, the ore is called run-of-mine material because there has been no treatment performed on it. There are three primary types of run-of-mine materials: Run-of-mine consisting of useful materials.

There are four main mining methods: underground, open surface (pit), placer, and in-situ mining.

Primarily, there are two types of mining methods being used for the extraction of minerals and ores – surface/opencast mining and underground mining.

The PSR report further illustrates the adverse effects of the mining of coal on the environment, water and human health. Coal mining leads U.S. industries in fatal injuries, and miners have suffered prolonged health issues, such as black lung disease, which causes permanent scarring of the lung tissues.

Mining techniques can be divided into two common excavation types: surface mining and sub-surface (underground) mining. Today, surface mining is much more common, and produces, for example, 85% of minerals (excluding petroleum and natural gas) in the United States, including 98% of metallic ores.

Galamseyers are people who perform illegal gold mining independent of mining companies, digging small working pits, tunnels, and sluices by hand. Galamsey is also referred to as Illegal Artisanal Small Scale mining (ASM).

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Illegal mining activities were identified as the cause of environmental problems such as water pollution, deforestation, poor soil fertility and limited access to land for agriculture productivity.

Spurred by widespread poverty and a lack of alternative income-earning opportunities, illegal artisanal mining is a well-documented phenomenon in sub-Saharan Africa.

Sub-Surface mining

Mining activities are associated with various social, economic and environmental impacts. There are however some social negative impacts associated with mining including violence, child labour, escalation of gender inequalities, health and environmental effects including deforestation and pollution.

Mining also has a positive impact on the economy of many countries. Another impact of mining can be measured in terms of employment opportunities and income generation. Commercial scale mining provides employment and skills transfer to more than 2 million workers.

Mining tends to raise wage levels, leading to displacement of some community residents and existing businesses, and elevated expectations (Kuyek and Coumans, 2003). Mining may also trigger indirect negative social impacts, such as alcoholism, prostitution, and sexually transmitted diseases (Miranda et al., 1998).

The extraction of minerals from nature often creates imbalances, which adversely affect the environment. The key environmental impacts of mining are on wildlife and fishery habitats, the water balance, local climates & the pattern of rainfall,sedimentation, the depletion of forests and the disruption of the ecology.