Bihar mica-bearing region

BIHAR MICA-BEARING REGION (RU: Бихарский слюдоносный район) is the group of the deposits of muscovite within India (Bihar state; with the length of 160 kilometres, with the width of 16-25 kilometres). It is being developed since the middle of the 19th century. The Bihar mica-bearing region is confined to the outcrop of the Archean crystalline schists, and of the gneissose granites, which are breaching these schists. The pegmatite veins of the plagioclase-quartz-muscovite composition are embedded mainly within the mica schists conformably with the stratification. The shape of the veins is lenticular, lamellar, tubular (the length is 20-90 metres, up to 300 metres, the thickness is up to 30 metres). The zones with large crystals of muscovite (up to 1.5 metres across) are situated on the boundary with the quartzous core and within the endocontact of the veins. The prospective reserves of mica are 10-15 million tonnes (1970).

The content of the muscovite with large crystalls is up to 180 kilograms per cubic metre, the yield of the sheet mica from the raw material is approximately 17%. Along the way, they extract beryl, columbite, and uraninite. The deposits are being developed by the small private open pit mines and by the underground mines, with the prevalent usage of the manual labour. The maximal depth of the development is up to 200 metres, the average depth is 15-20 metres. The mica is processed at the factories within the Kodarma and Giridih cities. The total extraction of the sheet muscovite is 6 thousand tonnes per year (1980). The Bihar mica-bearing region is the main supplier of the high quality sheet mica of the ruby colour (Bengali mica) into the worldwide market.