84 HOLLAND: MICA DEPOSITS OF INDIA. 



from falls of decomposed rock during the rainy season, a source of 

 expense which will continue, and become an increasing charge, as long 

 as simple open quarrying is continued and the sides allowed to remain 

 raw. In cases where there is a marked inclination in the dip of the 

 pegmatite-sheet, it will be more economical in the long run to 

 sink a shaft near the side of the quarry and reach the pegmatite by a 

 cross 'Cut, or, where the dip is not far from the vertical, the shaft 

 should be placed along the line of strike and the pegmatite worked 

 along drives with over hand stoping in all cases. 



The practice of sinking on the pegmatite — pursued both in the 

 Bengal worm-like mines and in the Nellore quarries — is giving rise to a 

 shocking destruction of good mica : a single blow with a pick, or a hole 

 bored for blasting through a mica " book " an inch thick, may result in 

 the loss of many rupees. It must be remembered that a " book" of 

 mica only one inch thick and six inches square weighs over 3! lbs. 

 and may be worth Rs. 15 to Rs. 20. A hole through the centre of 

 such a bundle would reduce its value to less than as many annas, and 

 the writer has seen many instances where such damage has been done. 

 Presumably every reasonable care is taken in the use of the pick and 

 in drilling holes ; but the present system of sinking on the pegmatite 

 in which the mica is concealed by the inevitable rubbish, always wet, 

 places the miner at a great disadvantage. With overhand stoping 

 the miner is able to keep a clean and dry working face, on which 

 the indications of a " book " are readily detected, and the mineral 

 removed without damage. But in addition to this more careful treat- 

 ment of the valuable mineral itself, there is a saving in necessary dead- 

 work ; for in blasting out the loose-textured pegmatite, the explosive 

 is assisted by gravity; the waste material is more than sufficient for 

 stowing the worked-out excavations, thus saving the cost of its 

 haulage to surface and removing the necessity of permanent timber- 

 ing in the winzes and rises; the work can also proceed continuously 

 instead of being interrupted by a luxurious cessation at nights and 

 during the monsoon, for water does not accumulate on the working 

 face of a rise. Even, however, if overhand stoping were adopted, the 

 ^ 74 ) 



