Sillimanite, Clay, Sand, Iron Ore, Copper, Gypsum & other minerals of Assam: Assam Geography
It is also an important mineral wealth of Assam. The Assam Sillimanite is in the form of massive rock from which cubes can been sawn for direct use in furnaces. 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. The largest boulder of massive Sillimanite in Assam and Meghalaya was estimated to weigh 300 tons. 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.
At present in Assam, it is found only in Karbi Anglong. It has a refractoriness of orton cone and is stated to be quite suitable for the manufacture of refractories.
It is known that fire-clays occur with coal measures of the Makum coalfield and that the Assam Railways and Trading Company prepared fire-bricks and refractories from these clays for their own requirements. Similar clay may be found in the Karbi Anglong Hills where the lower Eocene (Cherra State) coal, seam, etc., occur. It is also known that at the falls of the Nambor River in Golaghat district, such clays are available in Golaghat. There are thus extensive occurrences of these white clays in Assam wherever the lower Eocene beds are
In the alluvial tracts of the State the Potter’s clay is found in abundance. The Pottery industry, which mainly depends upon the availability of local clay, provides employment opportunities to a large number of persons. In the plains and valleys of the State, the pottery clay is the alluvial material found in the rivers and beds of bils.
Kaolin or China clay
Kaolin is found in good quantities in the Dora river of the old Lakhimpur district.
Deposits of fine-grained, white friable sandstones has been located in the coalfields of the Laitryngew and Cherapunji 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.
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.
Quartz-magnetic rocks are stated to be available in the Hahim area within Kamrup district. These rocks belong to the Dharwar system.
Copper minerals occur in the Umpyrtha and Ranighat areas in the Khasi and Jaintia hills and also in the Mahamaya hills in Goalpara district. It is mentioned in the Census Report of Assam,1961(General Report),that the occurrence of copper has been located in two places within Assam, one near Barduar in Kamrup district and another near Mahamaya Hills in Goalpara district. In both the places, the copper has been found in rocks of the Archaean age. On account of small and scattered show of the metal in both the places, proper investigation is required for exploitation of the same.
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. Felsper occurs in small quantity in the Karbi Anglong Hills in Assam.
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. During the Pre-British time this important material was collected in many rivers in Assam. A section of people, known as Sonowal Kachari was engaged for this purpose. Even now alluvial gold occurs in many rivers of Upper Assam such as Dikrong , Subansiri, Sisi, Dihing, Dibong, Noa-Dihing, Dhansiri, Disoi, Buridihing, Bhoroli, Burigong, Bargang,etc.. Although gold-bearing sand used to be panned in ancient items,it is now no longer an economic proposition.
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. Crystals of selenite have been found near Longloi in the Karbi Anglong Hills. It is known that gypsiferous shale occurs in the Dimasa Reserve Forest in the said district.
The dark-coloured Pyritiferous shales are found in several places from the coal bearing areas in the Lakhimpur district. It is suggested that these shales could be used for the preparations of alluminium sulphate and alum. For the proper utilisation of this economic material, an Alum plant is going to be established at Namrup.
In certain places within Cachar district brine springs occur and in the past salt was in the district. Salt was also made near Sadiya and Borhat in the undivided Lakhimpur district. But now-days due to the availability of salt at cheaper rates in market these difficult and remote places have lost their importance.
This mineral has been reported from some of the pregmatite veins in the gneissic area in the
Karbi Anglong Hills.