What is a Mineral?
Minerals by definition are naturally occurring inorganic solids formed through geological processes, possessing definite chemical compositions, atomic structures and specific physical properties. However this definition is not followed strictly. The term “mineral” is often used in a much more extended sense to include anything of economic value which is extracted from the earth. Thus, coal, chalk, clay, and granite though not being a mineral, are included in national figures for mineral production.
What is an ore?
An ore can be described as an accumulation of mineral in sufficient quantity so as to be capable of economic extraction. The minimum metal content (grade) required for a deposit to qualify as an ore varies from metal to metal. Many non-ferrous ores contain, as mined, as little as 1% metal, and often much less. Gold may be recovered profitably in ores containing only 1 part per million (ppm) of the metal, whereas iron ores containing less than about 45% metal are regarded as of low grade.
Where do we get minerals?
On analysis of Earth crust up to a depth of 3.5 km it has been estimated that eight elements account (oxygen, silicon, aluminium, iron, calcium, sodium, magnesium and potassium) for over 99% of the earth’s crust out of which 74.6% is silicon and oxygen, and only three of the industrially important metals (aluminium – 8.2% , iron – 5.6%, and magnesium – 2.3%) are present in amounts above 2% . All the other useful metals occur in amounts below 0.1%. Copper the most important non-ferrous metal, occurring only to the extent of 0.0055%. It is to be noted that the so-called common metals, zinc and lead, are less plentiful than the rare-earth metals (cerium, thorium, etc.). Thus we can say that if the minerals containing the important metals were uniformly distributed throughout the earth, they would be so thinly dispersed that their economic extraction would be impossible. However, the occurrence of minerals in nature is regulated by the geological conditions throughout the life of the mineral. Thus there are pockets of deposits of different minerals spread across the earth in different locations. There are minerals in sea bed also, which are yet to be exploited commercially.
Why Mineral Processing?
As mentioned above there are pockets of minerals, and generally minerals are associated with some particular types of rocks, which forms the gangue. Thus to get desired levels of minerals for further recovery of metals, the gangue (waste material) has to be economically separated from the mined ore. With dwindling resources and finite mineral resources available, the search is on for new deposits and for new technology to render marginal deposits economic. In the twentieth century mineral processing has developed as a serious and important professional discipline as a necessity, since without physical separation, the concentration of many ores, particularly the metalliferous ores, would be hopelessly uneconomic.
To reduce the cost of mined out ore transportation from mine to smelter, a mineral processing unit is installed at the mine site. The purpose is to separate the valuable minerals from the waste (gangue) minerals. This enrichment process increases the contained value of the ore to allow economic transportation and smelting. Moreover mineral processing also reduces smelter costs by reducing the amount of slag generation in the furnace due to impurities. In some cases the presence of some impurities may result in poor quality of metal and has to be completely avoided. Thus mineral processing is the need of the century.
What is Mineral Processing?
There are two fundamental operations in mineral processing: namely
. the release, or liberation, of the valuable minerals from their waste gangue minerals, and
. separation of these values from the gangue, this latter process being known as concentration.
Liberation of the valuable minerals from the gangue is accomplished by comminution, which involves crushing, and, if necessary, grinding, to such a particle size that the product is a mixture of relatively clean particles of mineral and gangue.
Concentration of ores can be done by one or combination of the following methods:
(1) Separation based on optical and other properties. This is often called sorting, which used to be done by hand but is now mostly accomplished by machine.
(2) Separation based on differences in density between the minerals. Gravity concentration
(3) Separation utilising the different surface properties of the minerals. Froth flotation
(4) Separation dependent on magnetic properties. Magnetic separation
(5) Separation dependent on electrical conductivity properties. High-tension separation
Why this page?
This page attempts to describe the equipments used in the Mineral Processing industry with their functioning and a short animation showing how the item works. This initiative has been taken to help the mining industry take calculated decision in mineral processing equipment selection, thus getting the most out of the investment in processing equipment and at the same time reducing the cost of mineral processing so as to be competitive in the market.