The mining wastes have different physical and chemical properties, which bring on various potential environmental influence.Different types of mining wastes are generated from according to the type of deposit and the technics used for mining and for ore processing or quarrying process. Mining wastes is the coarse or fine residues generated from the quarrying and processing of crushed-rock Aggregates. Sometimes, with proper disposal, these waste are saleable products, they have economic value. These recycled wastes could be used for site restoration, landscaping, construction etc. here are some common types of mining wastes.
Waste rock is unused extraction products generally stored for long period in a landfill site nearby the mining center, for saving transport costs. Generally, opencast pits and quarries generate much more mining waste than an underground mine. The main type of waste rock is generated by surface (or barren rock) stripping to expose the shallow ore. these barren rocks are generated by the passages (shafts, crosscuts). There are huge volume of waste rock are generated from mining and quarrying activities everyday.
Tailings (processing waste)
At a mine, an ore mill normally abuts on the extraction centre to produce the first marketable products (metallic concentrates, sorted ore, and ingots). The technological processes are very different according to the ore properties and various technics (flotation, leaching, and biotechnology). These units produce various types of waste, which can include:
- aqueous solutions from cyaniding,
- slurries of finely ground particles that have undergone one or more types of physical or chemical treatment, and which frequently contain one or more industrial additives that have participated in the conversion process (xanthates, miscellaneous salts, starch, etc.). These tailings are normally dumped in a sort of lagoon or settling basin within an embankment at the exit of the mill;
- in some case, atmospheric releases from sulphide roasting. Emissions to air would result in “environmental impact”.
Mill waste is generally referred to as tailings, or releases or effluents. It is generated by the various mining processes to meet final application demand. Waste is generated at all levels of the recovery process to upgrade the minerals, within the same process chain, and is considered as ultimate or stripped of useful elements.
Intermediate storage of products, ore stockpiles are not waste and are normally temporary dumps of lean ore at the mine site, depending on the cut-off content, which may vary with time. This type of mine project management is included in the overall mining plan. This management requires maintenance on the mine site for a period sometimes longer than a decade. Selectivity materials correspond to ores of lower grade than the limit assay. These ores have a content which, while lower than the limit content when stored, can be handled later without loss in the processing plant when it is not be saturated, in which case it is treated as lean ore.
In nature, the ores of metals such as iron, copper, lead, aluminium, and other metals are found in impure states, often oxidized and mixed in with silicates of other metals. During smelting, when the ore is exposed to high temperatures, these impurities are separated from the molten metal and can be removed. The collection of compounds that is removed is the slag. Slags are produced in many metallurgical operations throughout the world and are considered a by-product of the production of iron and steel.