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Mineral Processing Applications

Mineral processing, minerals beneficiation, ore dressing, are all names used for the step following the mine where an ore is processed. In general mineral processing is used on:

    (1) Metallic Sulphide ores;
    (2) Metallic Oxides ores;
    (3) Nonsulphide or non-metallic ores,
    (4) Free metal ores

Metallic Sulphide Ores

The primary method of processing sulphide ores is by froth flotation (following a multistage crushing and grinding). The best example of this is copper, where low grade sulphide deposits predominate and flotation is extensively used for producing a high-grade copper-sulphide concentrate low in iron. Much of the ore is of a finely disseminated nature, requiring carefully comminution to achieve liberation. There are often several different mineral forms and other metallics.

Molybdenum is often found with copper and is a common by-product that requires multi-stage processing usually by flotation to produce the necessary high-grade concentrate required. A considerable proportion of "Moly" production is acquired as a byproduct from copper concentration plants.

In the production of lead, zinc, and tin concentrates the important factor is the rejection of iron in the form of iron sulphides (pyrites). Flotation is the commonest process. As selectivity is important in the production of lead concentrates, it is usually necessary to have two or more cleaning stages in a lead circuit.

Complex cobalt sulphides and arsenides are recovered with flotation. The main problem in satisfactory recovery is close operating control. Controlled aeration of the pulp is very important when floating this mineral for it is usually associated with other sulphides.

The precious metals, silver, gold and platinum are frequently found associated with sulphides, arsenides and other complex ores. Flotation of these sulphides and arsenides is extensively used, particularly for silver ores. Gold tellurides are frequently found present in these complex mixtures and are also recovered in the flotation concentrates.

Metallic Oxide Ores

Iron is one of the main oxides and the concentration of iron ores has received widespread attention. Although magnetic separation, classification, and gravity methods have been used (and still are) in this field, flotation is widely used. Not only can a higher grade concentrate be produced by flotation but heretofore unworkable deposits are amenable to this process. Fine grinding is required to liberate the silica from the iron oxide and consequently the importance flotation.

The general application of titanium compounds in alloys, pigments, welding rod, and chemical warfare has created quite a demand for such minerals as rutile and ilmenite, the chief sources of this important element. Gravity, magnetic and electrostatic methods have been employed, principally from deposits in which the minerals occur in granular size. The necessity of working lower grade, more complex deposits, has expanded the use of flotation.

Processing of copper oxide ores presents both mechanical and metallurgical problems which, by careful analysis can been overcome primarily by hydrometallurgical processes in both heap leach and in full milling operations.


Non-metallics are processed to a large extent by froth flotation. By far the greatest present application of flotation in the non-metallic field is in the recovery of phosphate. Washing, screening, and classification are the common methods for recovering the coarse and pebble phosphate, but it remained for flotation to provide a satisfactory and low-cost means to reclaim and beneficiate phosphate formerly rejected as tailing.

The great demand for high-grade fluorspar, in particular that meeting the specifications for ceramic and acid grade, has been met, in part at least, by flotation, the most important recovery method.

Recovery of manganese minerals, because of their generally high gravity, is for the most part accomplished by gravity methods employing coarse and fine jigs and tables. Practically all manganese minerals are soft and therefore, losses by gravity methods leave considerable to be desired insofar as recovery is concerned. Then, too, some manganese ores are not amenable to gravity methods due to close association with impurities. This, of course, necessitates grinding, in some instances quite fine. Manganese flotation has been successfully employed for several years, although only on certain specific ores.

Coal is one the biggest users of gravity separation, featuring large (1,000 t/hr and larger) plants using multi-stage heavy media, and other gravity processes. The fines are often processed by flotation.

Graphite is perhaps one of the easiest non-metallic minerals to recover by flotation because of its natural floatability and water repellent action. It has been successfully floated as coarse as 10 mesh, which contributes much to the market value. Flake graphites are sold according to size with the coarser sizes commanding the highest prices.

The most important present-day commercial source of aluminum is from the mineral bauxite, a hydrous aluminum silicate, which usually has a variable composition and is associated with such impurities as clay, silica, iron oxide and titanium oxide. Present day production is generally from high-grade deposits and concentration depends to a large extent on washing plants to remove clay and other impurities.

Free Metal Ores

When people think of free metal ores they generally refer to gold and silver and the main processing is by gravity separation for small operations or by cyanidation for large. While in most operations recovery and extraction of free gold and silver is by means of cyanidation or gravity or a combination of these methods. However, flotation is sometimes necessary where certain physical conditions preclude the use of other processes. Notable examples are in extremely slow settling ores, as well as ores containing excessive cyanicides, soluble salts, or containing carbonaceous material. Direct flotation of gold and silver has been done, and is possible.

Diamonds, while not a metal, or processed mostly by gravity processes similar to small scale precious metal operations.

More information on specific processes is available at: A Mining Engineers Notebook: Mineral processing.


MIke Albrecht, P.E.

o   40+ years’ experience in the mining industry with strong mineral processing experience in precious metals, copper, industrial minerals, coal, and phosphate

o   Operational experience in precious metals, coal, and phosphate plus in petrochemicals.

o   Extensive experience performing studies and determining feasibility in the US and international (United States, Canada, Mexico, Ecuador, Columbia, Venezuela, Chile, China, India, Indonesia, and Greece).

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