Mineral Resources : Use and Exploitation – Environmental effects of Extracting and Using Mineral Resources – Case study
Producer – Chandan Gupta
Objectives :By the end of the session, students will be able to :
- Know about the minerals as an important gift of nature,
- Learn about the mineral status of India and uses of minerals,
- Appreciate the harmful effects due to over exploitation of these natural resources,
- Learn about classification of minerals,
- Know about mining activities, their disadvantages and control measures,
- Learn about the location of mines of some important minerals.
Introduction :
A Mineral is a naturally occurring substance having definite chemical composition, fixed internal atomic structural arrangement and formed by inorganic processes of nature. Both metallic and non-metallic minerals occur in nature. The natural assemblage of metallic minerals which can be exploited and extracted profitablyand serve as the commercial source of one or more metal values,are called Ores.All the minerals are non-renewable natural resources – it means that they are not replenishable. Once they are exhausted completely, they can not get back. These mineral resources are associated with rocks of the earth crust and obtained by surface and underground mining operations. As far as metals are concerned, they are extracted from their ores. Primary deposits of precious metals such as Platinum, Gold, Silver etc. are limited. At present India is largest consumer of Gold in the world. Silver will be finished by 2020. That is why the precious metals are becoming costly day-by-day. Minerals and metals play important role in the progress, development and prosperity of man and country aswell.
From the primitive to the most sophisticated modern man, in all stages of human advancement, man had to look to minerals for his sustenance, decoration, festivities and even for his funeral rites.
The primitive man in his efforts to hunt food as well as self protection started using hard rocks and minerals which he found so abundantly all around him. Hard rocks like quartzite and hard minerals like quartz, jasper, flint, chert etc. had been commonly used by him, either in their natural shapes or after crudely chipping them to some pointed shapes. The first metals the man used would be relatively soft hence metal like copper, tin, zincetc. were first utilized by him. These ages are known as the Copper Age and Bronze Age. Following the Bronze Age, the early man had learnt the use of Iron in its many forms, known as the Iron Age. The art and science of manufacture of Iron and Steel articles have developed in this country from pre-Vedic times and much faster thanthe other parts of the world. By the 3rd or 4th century A.D. during the period of Chandragupta II, India had been able to manufacture that marvel of pillar of rust-less iron which can be seen near Qutab Minar in Delhi even today.
India is self-sufficient in about 35 minerals and mineral substances which are used as basic raw materials in various industries. We have enough deposits of Iron, Copper, Alumina, Coal, Limestone etc. in Bihar, Jharkhand, Rajasthan, Chhattisgarh, Madhya Pradesh, West Bengal, Gujarat, Goa, Karnataka, Andhra Pradesh, Kerala in our country.
Our onshore [Ankleshwar, Krishna-Godavary Basin, Assam, Jaisalmer] and offshore [Bombay High] regions are rich in petroleum and natural gas resources. Heavier minerals like Ilmenite, Monazite, Uraninite, Zircon, Rutile etc. are concentrated in the form of thick Placers in beach zones. These placers are extended towards sea. Such placers on beaches and estuaries are mined for metals like titanium, gold, platinum, thorium, zirconium and even for diamonds. The well-known beach placers of Kerala coast are of economic importance and contain rich concentration of Monazite [primary source for metal Thorium] along with ilmenite and rutile.Ex-president of India Dr. A.P.J. Abdul Kalam suggested the use of Thorium in place of Uranium. Accordingly, by making some changes in nuclear power plants thorium should be used to generate electricity because, thorium is available in plenty in India whereas for uranium we are dependent on other countries.
Special mention is necessary about the possibility of metal accumulation on the sea beds. Continental shelf and adjoining areas of Indian Ocean are the favorable sites for this natural resource. The most spectacular are the deep-sea pelagic ferro-manganese nodules formed by various processes. Such nodules started to form during Cretaceous and attained maximum development during Pliocene and Recent period. Manganese content in these nodules is around 20 percent. In addition, they are known to contain valuable concentration of Copper, Nickel and Cobalt. Role of bacteria is considerable in nodule formation. In a report it is said that Manganese nodules in the Indian Ocean cover an area of over 10 million square kilometers and are next only to the Pacific Ocean.
Metallic and non-metallic mineral resources are to be extracted by surface mining as well as underground [both shallow and great depths] mining activities from earth’s crust. Before mining any deposit, differentactivities are to be undertaken which complete in different steps. They are :
- Searching Stage :Search of presence of minerals on the basis of various field and laboratory clues and guides etc.
- Exploration Stage : It means all phases of investigation carried out for a near realistic delineation of the three dimensional configuration of the mineral/ore body and assessing its economic potential, both in terms of grade and reserve [i.e. quality and quantity]
- Exploitation Stage :The bunch of operations commencing with the initial box-cut removal of the values to dispatching the produce from the pit to the utilization spot, comes under the purview of exploitation or mining stage.
- Extraction Stage :After mining, the ore minerals are in association with unwanted minerals. The techniques of liberation of wanted particles [the values] from the unwanted particles, reduction of mineral assemblage to an appropriate size, effective concentration of valuable part and rejection of gangue portion etc. for any smelting operation, come under this stage.
In India mineral search is done by Geologists, Geophysists, Geochemists etc. of various organizations of Government of India, Government of India Undertakings, Geology and Mining departments of State Governments, Corporations, Private sector companies etc. Some of the leading Geology and Mining organizations of India are :
- Geological Survey of India [GSI], Kolkata
- Oil and Natural Gas Corporation [ONGC], Dehradun
- National Mineral Development Corporation [NMDC], Hyderabad
- Coal India Limited [CIL], Kolkata
- Gas Authority of India Limited [GAIL], New Delhi
- Hindustan Zinc Limited [HZL], Udaipur
- Hindustan Copper Limited [HCL], Kolkata
- Gemological Institute of India [GII], Mumbai
- Cement Corporation of India [CCI], New Delhi
- Hindustan Petroleum Corporation Limited [HPCL], Mumbai
- Bharat Petroleum Corporation Limited [BPCL], Mumbai
- Indian Oil Corporation Limited [IOCL], Mumbai
- Oil India Limited [OIL], Assam
- Indian Bureau of Mines [IBM], Nagpur
More than 2100 mineral species have been discovered in nature. Every mineral has its own diagnostic properties on the basis of which it can be identified and distinguished with the others. Certain minerals have only one element in their composition such as Diamond and Graphite [only Carbon] whereas others have two [Quartz : SiO2; Fluorite : CaF2] or more elements [Orthoclase : KAlSi3O8; Apatite : Ca5[PO4]3F].
Uses of Mineral Resources :
Metallic [Ore] Minerals :
Bauxite [Al2O3.2H2O] :The principal use is for the manufacture of metallic aluminium [Al].This light metal has a high degree of strength and it can alloy easily with a number of other metals. Duralim, which is much favored is used in the manufacture of railway coaches, goods wagons etc. It is also used in the production of abrasives, refractories, chemicals etc. Aluminium sulphate or Alum is very much used in the paper industry and in water purification. It is a metal which combines lightness with strength and is highly resistant to corrosion. It is conductor of electricity hence it is being used in electric wires, cables etc. Its domestic use is for making utensils, thin foils etc. Lower grade of bauxite is used in cement industry.
Chalcopyrite [CuFeS2] :It is the most important ore mineral of metal Copper [Cu] which is a sulphide of copper and iron, also known as Copper Pyrites. The uses of copper are many. Because of its high electrical conductivity, its greatest utilization is in the electrical industry. Copper also forms a number of useful alloys – with Tin, it forms Bronze, with Zinc, it forms Brass, with Aluminium, it forms Duralumin etc. Salts of copper are used as disinfectants, fungicidesand for coloring glass.
Hematite [Fe2O3] and Magnetite [Fe3O4] :These are the two important natural iron oxides, serve as iron ores. After proper beneficiation, these iron ores, mainly hematite is used in iron [Fe] and steel making, as a heavy medium in coal-washeries etc. We utilize only small percentage of our iron ore production in our country. About 60 percent of our production of iron ore lumps are exported in the raw and unprocessed form to Japan andother countries. These countries prefer only our high grade ores. This trend may prove a serious drain in our reserves of high grade iron ores in the long run. Though we possesses vast reserves of high grade iron ores, now it is necessary to conserve our reserves of high grade iron ores.
Galena [PbS] and Sphalerite [ZnS] :In nature, the galena and sphalerite occur together.
The chief ore mineral of lead [Pb] is Galena – lead sulphide, PbS. It is also known as Lead Glance and Blue Lead. Silver sulphide is always present and therefore it is one of the most important source of silver. When sufficient silver is present, the ore is called argentiferous galena. The metal lead is being smelted from galena. The major uses of lead are in the manufacture of storage batteries, cable sheathing, lead pigments etc. Lead sheets, pipes, tubes etc. are manufactured. It is also alloyed with other metals to give rise to brass, bronze etc.
The chief ore mineral of zinc is Sphalerite – zinc sulphide, ZnS. It is also known as Zinc Blende and Black Jack.The metal zinc [Zn] is being recovered from sphalerite. Zinc is used for alloying, for galvanizing iron and steel, in the manufacture of white pigments, dry batteries, electrodes etc. Zinc compounds are extensively used in die-casting, in textiles, in rubber industries etc.
After the recovery of lead and zinc metals, silver and cadmium are also recovered as by-product.
Manganese Minerals :The chief sources of metal manganese [Mn] are the oxide minerals namely Pyrolusite [MnO2], Psilomelane [Hydrated oxide of Manganese], Braunite [Mn2O3] etc. In the manufacture of steel, manganese plays an important role. It is used as deoxidizer and desulphuriser during the manufacture of steel. Manganese gives extra hardness and resistance to abrasion. It is also used in making dry batteries, chemicals, in glass industry [for decolourising], in paints and varnishes [as a drier] etc.
Chromite [FeCr2O4]:The only source of metal chromium [Cr] is chromite, also known as Chrome Iron Ore. Chromite, an oxide of iron and chromium, is used as metallurgical, refractory and chemical purposes. Chromite forms useful alloys with iron, nickel or cobalt. With iron, it forms well known alloy Ferrochrome, which is used in making stainless steel. As a refractory material, it is used for making Chrome bricks, Chrome cement etc. for furnace linings [of copper and nickel smelting furnaces]. It is used as pigments, for the manufacture of chromates, dichromates etc. which are used in leather tanning and dyeing. It is also used in photographic materials, chromium plating etc.
Non-metallic Minerals :
Asbestos : Mineralogically, asbestos includes the fibrous forms of minerals of Amphibole Group. The fibers are generally long, fine, flexible and easily separated by fingers. The colour varies from white to greenish and brownish. The commercial value of the mineral depends on its property of being spun in to yarn, heat resistance etc. Larger fibers are used for fire-proof fabrics, brake-linings whereas shorter fibers are utilized in the manufacture of asbestos sheets, boards, roofing tiles, fire-proof paints, insulating cement etc.
Feldspar [KAlSi3O8, NaAlSi3O8, CaAl2Si2O8] :The feldspars are aluminous silicates of potassium or sodium or calcium. The feldspars are the most important group of the rock-forming minerals. Feldspars are used in the manufacture of glass, electrical porcelain insulators, for glazing pottery and ceramic wares, for making enamels etc.
Fluorite [CaF2] :It is a fluoride of calcium also known as Fluor Spar. It used as a flux in making steel, in the manufacture of glasses, for the production of hydrofluoric acid and its compounds, for the construction of lenses etc.
Graphite [C] :Like diamond it also has the composition of Carbon. It is also known as Plumbago or Black Lead. It is used in foundries and in the making of graphite crucibles. Because of very low hardness, it is used in the manufacture of writing pencils, lubricants, paints and pigments. It is also used in electrode making for the electric furnaces, atomic reactors etc.
Gypsum [CaSO4.2H2O] :Gypsum is a hydrated sulphate of calcium. It is utilized chiefly as a retarder in the manufacture of cement, in the manufacture of Fertilizer – ammonium sulphate, in the manufacture of Sulphuric acid, Plaster of Paris, sheets, boards etc. It is used extensively in the making of moulds in the ceramic industries. It is also used as filler in various materials such as paper, crayons, paints, rubber etc.
Mica Minerals :Because of excellent insulating properties and high heat-resistance, mica minerals are indispensable in the electrical industry. In nature, several varieties of mica occur such as Muscovite [potash mica], Biotite [iron-manganese mica], Phlogopite [manganese mica], Lepidolite [lithium mica] etc. Muscovite mica is mostly used for electrical insulation, thermal insulation etc.
Phosphorite [P2O5] :Phosphorite is of commercial importance in the manufacture of fertilizers, elemental phosphorus and phosphoric acid.
Talc [Mg3Si4O10(OH)2]:Pure talc is a hydrous metasilicate of magnesium and it is the most familiar mineral to mankind. It is served as a base in cosmetics [talcum and face powders] and toilet preparations. It is used as extender in the paint industries, as a filler in the rubber, paper and textile industries.
Wollastonite [CaSiO3]:It is calcium meta silicate and also known as Tabular Spar. The largest use of wollastonite is in the ceramic industries. Other important uses are in the agriculture, paint, paper industries. It is also used in thermosets and thermoplastics.
Barite [BaSO4]:It is sulphate of barium and chief source for metal barium. On account of its high specific gravity [4.5], it is also known as Heavy Spar. The pure, white variety is much favored in the manufacture of white paint, in the production of wall papers, also used in textile and leather industries. Off colour barites are used in petroleum prospecting operations [as weighting drilling muds in rotary drilling]. The metal barium forms a number of useful alloys with aluminium, magnesium, nickel. Salts of barium especially barium sulphide, which is used as barium meal, to x-ray for the inside examination of stomach, intestine etc. Barium chloride is used for water softening also.
Calcite [CaCO3]:This mineral, carbonate of calcium, is one of the widely distributed minerals in nature and also known as Calc Spar. There are many varieties of this mineral of which pure, colourless, transparent variety known as Iceland Spar, is important in the optical instruments. Calcite finds an increasing use in the textile, paper and rubber industries as a filler and its super white quality is being used for the manufacture of insecticides, distempers, paints etc. It is also used in glazing pottery, for the manufacture of calcium carbide, bleaching powder, glass, soap, paper etc. and as a flux in metallurgical operations [mainly smelting].
Preciousand Semi-precious Stones :
When the minerals are sparklingly occur in nature, mainly in difficult terrains, deep jungles with rarity, they are treated as Precious stones. They are properly cut, polished and used in jewelry as Gemstones.
Precious stones are predominantly single crystals or grains, their varied colours brilliance and transparency, made them attractive for ornamental purposes. They have certain specific qualities which make them precious and valuable. The important precious minerals are :
Diamond [C] :Diamond is a pure form of carbon and the hardest mineral known. If colourless, transparent and flawless, it is the most precious among the gem stones. The opaque diamonds which are not well crystallized, are used extensively as abrasives and cutting purposes in gem-cutting, diamond drilling tools, for dressing emery wheels etc.