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.
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.
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.
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.
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.
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.
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
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.
Copper minerals occur in the Umpyrtha and Ranighat areas in the Khasi
and Jaintia hills and also in the Mahamaya hills in Goalpara district.
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.
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
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