Minerals are formed over a period of millions of years in the earth’s crust. They are derived from rocks, which form the earth’s crust. They are of different kinds, for example, salt, coal, petroleum, quartz, bauxite, iron, copper, gold and diamond. They are broadly grouped as metallic and non-metallic. Mineral ores containing metal are known as metallic minerals. The remaining minerals are called non-metallic. Gold, copper, silver, tin, aluminium and iron are examples of metals. Those metals occur in combination with other mineral components are called ores. Metals are separated from the ores by using heat. This process is known as smelting. Coal and petroleum are used as sources of energy. Quartz is used extensively in the production of glass, electronic circuits and silicon chips. Most of the minerals are associated with the igneous and metamorphic rocks of the Deccan and parts of Bihar, Odisha, M.P., Rajasthan and Assam as well as some parts of the Himalayan region.
It is estimated that India has about 1/4th of the world’s known iron-ore reserves. The iron-ore reserves of Bihar and Odisha are among the best in the world. These two states together produce a major share of the country’s total iron-ore production. A.P., M.P., Maharashtra, Tamil Nadu and Goa also have important reserves. Manganese is used in the manufacture of special varieties of steel. It helps to harden steel. Major deposits of manganese are found in Karnataka, Odisha, M.P., Maharashtra and Goa. India is one of the largest producers of manganese in the world. Bauxite deposits are found in Bihar, M.P., Gujarat, Odisha and Maharashtra. Aluminium is extracted from bauxite. This metal is light in weighty and is used in the manufacture of Aeroplane and electric wire. Bihar and M.P. are the major producers of Bauxite in the India. Copper and gold deposits are found in Singbhum district (Bihar), Balaghat (M.P.) and Jhunjhunu and Alwar districts (Rajasthan). Gold is found mainly in Karnataka. Its Kolar gold mine is one of the deepest mines in the world.
Mica, gypsum, limestone, diamond and salt are some important non-metallic minerals found in India. India is the world’s leading producers of mica. Bihar, A.P., and Rajasthan are the main producers. Gypsum is mainly used in the manufacture of fertilizers, cement and Sulphuric acid. Nearly 4/5th of it comes from the desert region of Rajasthan. Limestone is used in the smelting of iron ore as well as manufacturing of cement and mortar. It is found mainly in the states of Bihar, Odisha and M.P. Diamond is a precious gemstone known for its brilliant lustre, transparency and hardness. They are used for industrial purpose as well as for making jewellery. They are found in A.P. and M.P. India is the largest exporters of processed diamonds. Sea salt is obtained along the coasts of Gujarat, Maharashtra, Tamil Nadu and A.P. more than half of the sea salt is made along the Gujarat coast. The sea salt comes from Sambhar and Didwana lakes.
Rock salts come mainly from Mandi district in Himachal Pradesh. Coal and petroleum being associated with fossils which were once part of living organisms, they are also called fossil fuels. Coal is formed from decayed plants buried along long ago in swamps. Fresh plant matter is 80% of water and 20% carbon. During the process of change from wood to coal, the concentration of carbon gradually increases. Peat is the first stage of coal development. It is dark brown in colour. It has about 33% carbon content.
Lignite is the next stage of coal formation, which has nearly 50% carbon. If the process continue, lignite become sub-bituminous, bituminous and eventually anthracite coal. Anthracite has more than 85% carbon. It is the best quality of coal. It is very hard, compact, and black in colour, ignites slowly and burns with a short blue flame. Petroleum and mineral oil is found in the pores of sedimentary rocks. It has an organic origin, i.e. form animal and plant maters contained in shallow marine sediments such as sand, silt and clay.
In India, petroleum is found in Gujarat, Maharashtra and the Brahmaputra and the Surma valley in Assam. It is believed that oil-bearing state may also located in other parts of the country such as the deltas of the Ganga, the Mahanadi, the Godavari, the Krishna and the Kaveri. The Bombay high, 160km away from Mumbai in the Arabian Sea is the largest producer of petroleum in the country.
Uranium and the thorium are the important source of atomic energy. We have large deposits of uranium in Bihar and Rajasthan. The monazite sands found along the coast of Kerala produce thorium.