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Assam is endowed with vast mineral resources. The major minerals like coal,
oil and gas, limestone, dolomite, sillimanite and corundum, iron ore, felspar,
glass-sand, refractory and fire clays, kaolin, beryl, gypsum, pyrite,
vermiculite, salt, copper, gold etc. have been reported to occur in the state.
The most important minerals being exploited so far in Assam are coal, oil and
gas, limestone and sillimanite.
Coal
In Assam, coal occurs in Garo hills, Khasi and Jaintai
hills, Mikir hills, Jaipur and Makum. The tertiary coals of Assam are
remarkably low in ash but high in sulphur. Assam coal is being consumed
at present by the railways, iron and brass foundries, brick kilns, inland
water steamer services, tea gardens and other industries in addition to
household consumption. Apart from its general uses, Assam coal is eminently
suitable for the manufacture of coal distillation products.
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Oil and Natural Gas
The oil producing areas of Assam lie in the upper Assam valley
and are geologically confined to the Tertiary Strata - mainly Oligocene.
Assam is first state in the country where oil was struck in 1889 at Digboy.
At present oil is being tapped at two areas - the Digboy and the Naharkotiya
and Moran fields. Two more refineries of considerable size have
come up in the public sector at Gauhati and Barauni and the third with
a petrochemical complex is under way. A new refinery, Numaligarh refinery
(3m. tones capacity) was commissioned on July 9, 1999. The availability
of associated natural gas is dependent on the extraction of crude oil.
Vast quantities of natural gas are being produced along with the production
of crude oil. Only two projects under the "utilization of natural
gas scheme" have so far come up in the state. These are the thermal
power plant and the fertilizer factory at Namrup.
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Limestone
The high-grade fossil limestone or 'nummulitic' limestone deposits
of Assam are geologically known as 'Syket limestone' as these belong to
that groups of rocks. The limestone deposits are confined in areas of
Garo hills, united Khasi and Jaintia hills, Cachar hills and Mikir hills.
One of the largest outcrops of limestone is at the foot of the Khasi hills.
Vast deposits of high-grade limestone are best observed in the Jowai area.
Lime stones of the Khasi and Jaintia hills can be used for manufacture
of cement and for lime-burning purposes. It can be used in chemical industries
and for metallurgical purposes. The limestone deposits of the state offer
vast scope for developing innumerable industries where limestone is required.
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Sillimanite
The sillimanite deposits of the Nongstoin state in the Khasi
hills are world famous from the point of view of quantity and purity of
the mineral. Assam is the major producer of this mineral in India and
contributes more than 90% of the total production. Corundum is found to
occur in association with the sillimanite deposits. Low-grade 'quartz-sillimanite
schists' also occur in the same area.
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Clay
Assam is endowed with fairly large reserves of sedimentary white clays as
well as Kaolin or 'China clay', which forms an important basic raw material for
ceramic or refractory industries. These Clays are found to occur at many places
in the Garo hills, Khasi and Jaintia hills and the Mikir hills. This clay is
quite suitable for the manufacture of medium to low-grade white wares and other
ceramic products like stoneware pipes, sanitary ware, glazed tiles and bricks.
The Kaolin deposit near Mawphlang is found to be as good as the Kaolin of corn
wall.
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Glass Sands
Deposits
of fine-grained, white friable sandstones has been located in the coalfields of
the Laitryngew andCherapunji areas. The friable quartzite of the
Shilllong series around shillong and the Tura sandstones of the Garo hills are
suitable for manufacture of sheet glass and fruit glass after washing.
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Iron Ore
Occurrence of banded-iron ore have been located in the
Chanderdinga hills and Abhayapuri areas in Goalpara district and in the
Aradanga-Rangchapara areas on the border of the Kamrup and Khasi and Jaintia
hills districts.
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Copper
Copper minerals occur in the Umpyrtha and Ranighat areas in
the Khasi and Jaintia hills and also in the Mahamaya hills in Goalpara
district.
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Felspar
Felspar is a common mineral found to occur in association
with granites. Recently workable felspar deposits have been recorded near
the Hahim area in Kamrup district.
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Gold
Gold
is reported to occur in sands, gravels and alluvial terraces along some of the rivers
in the Lakhimpur, Sibsagar and Darrang districts of Assam.
A gold-bearing rock was located at a place about 5 miles southwest
of Mawphlang.
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Gypsum
Gypsum in the form of selenite crystals and disseminated in
shale beds occur at Mahendraganj in the Garo hills and at a few places
in the Mikir hills.
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