Gold is very precious metal, serves as the most vital element in international transaction and larger portion of gold is used in monetary systems. Gold occurs in India in quartz veins or reefs of quartz traversing igneous, sedimentary or metamorphic rocks.
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More often it gets liberated by weathering and particles of gold get concentrated in rivers and streams and at certain places, such deposits are known as ‘placer such deposits are known as “placer deposits’ from which gold is recovered by panning.
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The principal sources of this precious metal in India, however are the quartz reefs traversing the Dharwar rocks of Kolar district (Karnataka) which are auriferous at a few places?
A small quantity produced at the Hutti mines in Raichur district is released for Industrial purposes through State Bank of India. The main problem with the Hutti mines is the low grade of ore quartz veins and lenses in the Dharwad schists including hornblendic and chloritic schists and amphibolites, contain most of the country’s reserves of gold ore.
Production and Distribution:
A large quantity of gold is used in the country for the manufacutre of jewellary, dentistry and decorative articles. There are three important fields in the country namely Kolar Gold Fields, Kolar district, Hutti Gold Field in Anantpur district (Andhra Pradesh). Total in situ reserves of gold ore are estimated at 22.4 million tonnes, with 116.50 tonnes of metal.
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The production of primary gold at 2239 kg (excluding by product gold recovery from imported concentrates) in 2010-11 registered increase of about 7.44% as compared to the previous year. Karnataka was the leading producer of gold accounting 99% of total production.
The investigation of gold at Parasi, Ranchi district, Jharkhand has established a resource of 1.51 million tonnes of gold ore with an average grade of 2.47 g/t gold. Gold ore resources have also been established at Pahardia block, west Singhbhum district, Jharkhand and Ajjanahali east block of Tumkur district, Karnataka.
Karnataka:
99 per cent of the Indian gold comes from the State of Karnataka. In 2010-11 the auriferous lodes of these goldflelds are contained in the quartz reefs traversing the Dharwar rocks of Kolar district. The quartz veins run parallel to one another in a north-south belt of hornblende-Schists along shear-zones. The gold is associated with pyrite, pyrrhotite and arsenopyrite, the ore being hypothermal in origin.
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The most productive of these is a single quartz vein, about 1.2 m thick, which bears gold in minute particles. Mining operations in this reef have been carried out since 1880’s to depth beyond 3,000 m, some of the deepest mining shafts in the world. They have disclosed continuance of the same mode of distribution of the ore in the gangue. Gold is obtained by crushing and milling the quartz.
There are ancient mines of gold at Honnali, Lakkavalli Kempinkote and other places in Shimoga, Chikrnaglur and Hassan districts, at Bellary in Tumkur district and at Gadag in Dharwar district which call for further investigation.
During recent years, the Geological Survey of India has carried out detailed surface and underground investigations in the Kolar goldfield area with a view to locating new lodes. Gold mineralised over a strike length of 200 million has been established in a vertical shift area of Kolar gold patch.
There are four mining centres in the state viz. Nandydroog, Mysore, Oregaum and Champion reef. In Kolar district, thousand tonnes of gold ore having 17,738 kg of gold content (metal) have been proved. Recently 743 kg of gold valued at 30, 56, 32 thousand rupees has been produced in Kolar area.
Next to Kolar, but far below it in productiveness, is the Maski band of Dharwad rocks which has gold ore occurrences in the Hutti mine. It produced 595, 3 kgs of gold in 1915, but the output fell off and the mine was closed.
When they were reopened in 1948, the working had reached a depth of 305 m. This and other abandoned gold workings in the area are receiving the attention of the Government and have found mention in the Third Plan of the Government of India. Gold, mineralized over a strike length of 200 m, has been established in a vertical shift area of Kolar gold patch.
The state of Karnataka has a recoverable reserve of 7,504 million tonnes of gold ore and 42,023 kg of metal. These estimates are from the districts of Kolar, Dharwar, Hassan and Raichur.
Andhra Pradesh:
Gold ore is also found in the Ramagiri fields in Ananatapur district of Andhra Pradesh where mineralisation extends for 19 kms from north to south from Kanakapuram to Jibutil. Gold was mined at Ramagiri till 1924, when the mine was abandoned due to depletion of ores.
On the basis of the detailed mapping done by the geological survey of India in the recent years, a total of 7.06 million tonnes of ores and 37,025 kg of gold metal has been assessed in the state. The other areas of gold mines are Bisanattam and Palachchur in Chittoor district and Johnagiri in Kumool district.
Bihar:
Gold has been obtained from the alluvium of the rivers and streams of southern Chotanagpur. The Subarnarekha (gold streak) river as its name suggests, is well known for the gold content of its sands. After heavy rains the local villagers wash and obtain from the river and stream sand small quantities of gold. Besides Subarnarekha, Sone nadi in the Singhbhum district and the streams draining the Sonapat valley have gold contents in sands.
Occurrences of gold are reported in the Archaean quartzites near Lowa in the Singhbhum district. Some other abandoned mines are located in the Chotanagpur area. There was recovery of gold from copper slime at Ghatsila copper smelter of HCL, at 111 kg in 1986.
Madhya Pradesh:
Gold has been obtained from times immemorial by local gold washers from river sands and gravels from parts of the districts of Balaghat, Bastar, Bilaspur, Jashpur, Mandi, Raipur, Raigarh and Seoni. The only localities where gold has been found in situ are Sonakhan in Bilaspur district and Sleemanabad in Jabalpur district, where it has been found in small quantities in copper-ores.
Maharashtra:
The Geological Survey of India had expanded its search for gold from the century-old Kolar goldfield to the newly-located gold-bearing zone at Kolari in Maharashtra. Geologists had identified gold associated with scheelite in the Kolari area which opened up a -new vista of exploration for the two metals.
In the Kolari Mahabardi and Pular-Parsori areas, a very promising gold vein near Kolari was also spotted. Encouraged by this, the GSI had drawn up a two-phase programme for intensive search for not only the gold-scheelite association but also for other possible minerals in the areas.
Tamil Nadu:
A few quartz veins traversing a band of the chloritic and argillaceous schist’s of Dharwar age support Anantpur field whose yield in 1915 approached 6804.4 kg. After several vicissitudes this mine ceased operations in 1927.
The chief gold-bearing belt is the Wynad goldfield in Gudalur taluik of Nilgiri district, where there are gold mines and prospects which were opened up during 1890 and subsequently abandoned.
Gold is also known to occur at Bensibetta hill tracts in Gobichettipalayam taluk of Coimbatore district and in some parts of Dharmapuri and Krishnagiri taluk of Salem district.
These areas merit detailed investigation. At the above and other places in peninsular India, the former existence of gold is revealed by many signs of ancient gold-working in diggings, heaps of crushed quartz and stone mortars, which have (as has often happened in India with regard to other metalliferous deposits) guided the attention of the present workers to the existence of gold.
Alluvial Gold:
It can be seen that vein-gold occurs in limited areas. The distribution of alluvial gold in India, however, is much wider. Many of the rivers draining the crystalline and metamorphic tracts in India, are reputed to have auriferous sands, but only a few of them are commercially important. Alluvial gold-washing is carried on in the sands and gravels of many of the rivers of Madhya Pradesh and in sections of Indus Valley at Ladakh, Baltistan and Gilgit, but none of them is of any appreciable richness.
The only instance of successful exploitation of this kind is the dredging of the upper Irrawardly in Burma for several years; in this way some 141 to 170 kgs of gold were won a year, but the returns fell off and the operations were closed down in 1918. The production of gold in 2003-04 was 3363 kg. India’s demonstrated recoverable reserves (proved and probable) of gold are estimated at 50,008 kg from Karnataka and Andhra Pradesh.