Minerals are unevenly distributed over the earth's surface. Some of the old plateaus and mountains, which have been eroded for millions of years, now contain valuable metallic minerals, which are now exposed on the surface or occur as result of weathering. The Canadian shield, the Ural mountains in Russia, the African plateau in Zaire and South Africa, the Deccan plateau in India are rich in minerals Some of the sedimentary basins contain coal or petroleum or natural gas.
The discovery of minerals and their exploitation has often led to rapid economic development of the region. For example, the 'gold rush' led to the development of California in the United States and settlement of people in Australia and parts of South America. The discovery of copper ores in the Katanga region of Africa led to the construction of railways and economic development. The discovery of oil in the Persian Gulf region has led to a spurt in development in the Middle East. Unlike agricultural or pastoral activity mining is of short duration, which may last for a few years or few decades depending on the size of the ore and other factors.
Minerals are usually classified into the following type:
(a) Salt, sulphur, phosphate, asbestos and precious stones like diamonds
(b) Building stones - serpentine, limestone, marble, granite, sand and clay
(4) Atomic minerals - uranium and thorium
9.41 Iron Ore
Iron is an element found generally in nature in chemical combination with oxygen, sometimes with carbon, water and with sulphur. It mostly occurs in the iron-oxygen compounds found along with earthy materials called gangue. Iron is extracted from its chemical compounds, and separated from the impurities. This is commonly done in a blast furnace using coke (carbon), hot air (oxygen) and limestone. The residual impurities are removed in a specially designed furnace. Iron ore with less than 30 per cent metallic iron content can be used only if concentrated or beneficiated by calcination, roasting, weathering or washing.
Types of Ore: There are four varieties of iron ore
(i) Hematite F2O2: It is the most important source. It contains about 70 per cent metallic iron. Moisture content is low, 1 percent and colour is black to brick red.
(ii) Limonite 3Fe2O3 3H2O: It contains about 59.89 percent iron with moisture content of about 11 per cent. The colour is yellowish, and red when heated.
(iii) Magnetite Fe3O4: This is the best type of ore with an iron content of about 72.4 percent. The moisture content is the lowest in such ore, about 0.3 percent. The colour is black.
(iv) Siderite FeCO3: it is of yellowish or brown colour having a metallic content of 48 per cent. Moisture content is 0.7 percent.
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