The two metals lead and zinc rarely occurs in native state, they generally occur in combination with other elements. The ore minerals of lead and zinc are usually found to occur in association -with each other. The followings are the important minerals of lead and zinc:
Origin:
Lead and zinc ore minerals, particularly the sulphide zones are formed due to contact metasomatism, replacement by hydrothermal solutions.
Mode of occurrence:
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Most of the lead ore mines of the world are also zinc ore producers and nearly all zinc ore deposits carry lead ore. Both lead and zinc ore bodies usually occur as veins and massive or tabular lodes, and as disseminations, mostly in, limestone or dolo nites. Majority of these ores occur as cavity-fillings and replacements formed by low-temperature hydrothermal solutions.
Distribution in India:
The most important lead-zinc deposits of economic value in India is the Zawar deposit of Udaipur district of Rajasthan. India’s reserve of these ores is meagre compared her needs.
In the zawar area, the Mochia Magra, Baraj Magra and Zawar Mala hills contain most extensive deposits.
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The Zawar mine is located in the Mochia Magra hills. The principal rock type of zawar area consists of phyllites, slates, mica-schists dolomites and quartzites of the Aravalli system. But mineralisation of lead and zinc sulphides is solely confined to the dolomites whereas adjoining phyllites are almost barren. The lead and zinc deposits are confined to the upper series of the Aravallirocks in the zawar area. The localisations of the ores are structurally controlled by the shear zones. The ores occur in shear zones and follow shear planes which are the youngest tectonic feature in the area.
Most of the ore-shoots are found to occur as irregular steeply dipping and thin Parallel tabular masses. Galena is generally concentrated in some particular portions of the deposits but the sphalerite is more or less evenly distributed. The gangue is dolomite and quartz.
Evidences obtained so far suggest the formation of the Zawar lead-zinc deposits from hydrothermal solutions at about 250°C.
The ore minerals consist of argentiferous galena associated with sphalerite containing a small percentage of cadmium, pyrite, arsenopyrite and chalcopyrite. The ore contains 1’5 to 2% of lead and 4–5 to 5% zinc.
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Other important occurrences in the country are as follows:
(a) Lead copper ore deposits in Agnigundla area of Guntur district of Andhra Pradesh.
(b) Lead-zinc copper belt of 3-km long in Ambamata-Devi area of Gujarat and Rajasthan.
(c) Sargipalli area in the district of Sundergarh (Orissa).
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The estimated reserve in the country is about 9 million tonnes.
Economic uses:
(i) Lead is used in the construction of accumulators, for lead piping and sheeting, cable covers, as pigments in glass making, in medicine etc.
(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), in the manufacture of batteries and electric appliances. Besides, they are widely used in textile industry, timber preservation etc.