86 Mr. T. H. Holland — Mica-hearing Pegmatifes. [July, 



The large size of the crystals facilitating their extraction makes 

 some of these minerals, like the phosphates and felspar, worth attention 

 from an econotnic point of view, whilst the most valuable constituent of 

 all, mica, is of value purely because of the large size of the sheets it 

 forms. Crystals or "books " of muscovite-mica have been obtained in 

 Nellore District, measuring 10 feet across the basal planes, but usually, 

 of course, they are much smaller, all gradations of size being obtained 

 from those of mai-ketable value down to scales of microscopic dimensions 

 such as occur in the common massive granites. Being the most delicate 

 mineral in the rock the mica is the first to show the effects of crushing 

 earth-movements, and large quantities of valuable mineral have by 

 these means been destroyed, but it is on account of the remarkable 

 stability of the Indian peninsula, the geologically long and perfect 

 quiescence it has enjoyed, that India is able to boast of the finest mica 

 deposits of the world. 



In India, as in the mica-mining areas of America, the pegmatites 

 are found associated with mica-schists, quartzites and other schistose 

 rocks of the so-called upper division of the Archtean group. Into these 

 schists the pegmatites have been intruded, generally along^^ but some- 

 times across, the folia, in the form of thin sheets, lenticular bodies- or 

 large thick bosses. The common disposition of the mica-bearing peg- 

 matites in sheets seems to have been entirely overlooked by the 

 Hiiners in India, and ignorance of this fact is the principal cause of the 

 exceedingly wasteful and primitive .system of mining now being 

 practised under European as well as Native management. 



In the districts of G-ya, Hazaribat^h and Monghyr the so-called 

 mines are narrow, irregular holes, following the pegmatite sometimes 

 to depths well over 200 feet. The whole of the materials — mica, 

 rubbish and water — are brought by a string of coolies up to the mouth 

 of the hole, which is often near the summit of. a hill, being the point 

 wliere, on account of better exposure, the pegmatite outcrop was ori- 

 crinally discovered. On account of the accumulation of water, all 

 mining operations are suspended during the monsoon season, and at the 

 close of the rains the process of "forking" a mine occupies several 

 days and sometimes weeks. In the same way, an hour every morning 

 is spent in baling out the water accumulated overnight. With the one 

 exception now being inaugurated at Bendi, thei*e is not a single 

 vertical shaft in the whole mica-mining area of Bengal, not a single 

 drive or cross-cut to show that the miners have appreciated the actual 

 disposition of the pegmatite as normal intrusive sheets, and, notwith- 

 standing the favoui-ably- shaped natural contours of the ground, not a 

 single adit for the removal of water. That mica-raining has yielded 



