In appearance, vermiculite looks like mica, but the physical and chemical properties are a bit different. On heating, vermiculite swells up and exfoliates into thin sheets; the swelling may be twenty times or more. The swelled-up vermiculite is very light and thus may be used as an ingredient for the making of light cement or plaster. Vermiculite is also used in the packing industry and the making of insulator against heat and sound.
Composition and origin: Chemically vermiculite is like phlogopite, its composition being hydrated magnesium silicate. It is supposed to represent a hydro-thermal alteration of biotite or phlogopite. Its colour may be yellow, brown or blue. It is very soft, and slippery like soap.
Occurrences in India: The reserves of vermiculite are limited. Deposits of vermiculite are found in the states of Andhra Pradesh, Karnataka, Gujarat, Tamil Nadu, West Bengal, Madhya Pradesh and Rajasthan.
Andhra Pradesh: Vermiculite is available in the district of Nellore, where there are 4 working (private) mines. The reserve of vermiculite is this district is about 52834 tons. The colour of vermiculite here is bronze yellow. Andhra Pradesh produces about 500 tons (40 per cent) per year.
Tamil Nadu: Tamil Nadu produces about 60 per cent India’s total production of vermiculite. Good-quality deposits of vermiculite Are mostly found in the North Arcot district, where there are a few working mines. The total reserve of vermiculite in Tamil Nadu (North Arcot district) is about 116500 tons. The average annual production in Tamil Nadu is about 850 tons.
Karnataka: Vermiculite is found in the districts of Hassan, Mandya and Mysore, the total reserves there being about 22140 tons, 1000 tons and 23325 tons respectively.
West Bengal: Vermiculite occurs in the district of Bankura, where there is a mine with a small production. The vermiculite recovered from this mine is mainly used for making insulators. The total reserve of vermiculite in West Bengal is about 3456 tons.