Wednesday, November 4, 2009

Metalic Minerals: TIN, LEAD and ZINC

TIN The main ore of tin 'is cassiterite or tinstone with about 75 per cent of tin. It occurs in igneous and metamorphic rocks. Nearly 80 per cent of the world's supplies come from alluvial deposits.
Distribution in the World Malaysia is the world's leading producer and exporter of tin. Other producers are Chma, Indonesia, Thailand, Nigeria, Zaire, Bolivia and Australia.

Distribution in India In India, Bihar, Jharkhand and Rajasthan are main l?roducers of tin.

5. LEAD AND ZINC The two metals, lead and zinc, rarely occur in native state. They generally occur in combination with other elements. Galena is the chief ore of lead while sphalerite or zinc blende is the chief ore of zinc. These sulphide ore minerals of lead and zinc are formed due to contact metasomatism, replacement by hydrothermal solutions. Galena is found in veins in lime­stones, calcareous slates and sandstones and occasionally in metamorphic rocks or in association with volcanic rocks, while zinc blende or sphalerite is found in veins in asso­ciation with galena, chalcopyrites, iron pyrites and other sulphide ores. The chief rock types associated with the sulphide ores of lead and zinc are pyrite, slate, dolomite and quartz.
Economic Uses (i) Lead is used in the construction of accumulators, for lead piping and sheeting cable covers, as pigments in glass making and in medicine.
(ii) Zinc is used for coating, galvanising iron and steel products, in the manufacture of pigments and alloys with other metals (like brass, bronze, german silver) and in the manufacture of batteries and electric appliances. Besides, it is widely used in textile industry, timber preservation, etc.
Distribution in the World Major producers of lead are the USA, Russia, Australia, Canada, Peru and Bulgaria. Leading producers of zinc are Canada, Russia, Peru, Aus­tralia and the USA.

Distribution in India Given below is a statewise survey of lead and zinc resources in the country.

Rajasthan Here, lead and zinc are extracted from the Zawar mines in Udaipur district and from Anguncha­Rampura in Bhilwara district. In these mines, silver ore is also extracted.

Andhra Pradesh Cuddapah district has the reserves. Gujarat Here, lead and zinc are extracted from Banaskantha, Vadodara, Panchmahal and Surat.

Lead and zinc reserves also occur in Meghalaya and Sikkim.

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