56 HOLLAND : MICA DEPOSITS OF INDIA. 



similar in character and origin to the schists with which the mica is 

 found in Nellore and in Bengal. Pegmatite-veins are occasionally 

 found in the Mercara schists, and towards the south-eastern end of the 

 belt, near Pollibetta, these have been found to carry muscovite, which, 

 though excellent as regards freshness and elasticity, is often damaged 

 by pressure-figures and is warped. The rocks are largely covered by 

 cultivation of the thick soil-cap for coffee -growing ; consequently the 

 exposures are very few, and only traceable for short distances. Two 

 definite occurrences of mica in sheets of marketable size have been 

 opened up near Pollibetta. On the Beechlands Estate, Mr. H. G. 

 Parsons obtained pieces 6 to 8 inches square, some of it, but a very 

 small proportion, of excellent quality. On Elk Hill, Mr. J. Chisholm 

 obtained much larger pieces from a pegmatite-vein in his estate. Six 

 lots of these sent to London were valued by a firm of mica brokers, 

 and were estimated to be worth from a few pence to 8 shillings and 

 6 pence a pound. The mica was cut to rectangles measuring I2"x 

 14", 9"XI2", 6"xo/', 5"X7", and various sizes of narrow ribbons. 

 The results obtained by this experiment are very encouraging, and, as 

 long as the vein can be definitely traced, it might be advisable to sac- 

 rifice the coffee land for mica- mining ; but it would be highly indiscreet 

 to destroy good coffee land for mere prospecting operations, as peg- 

 matites in schists so disturbed are likely to be very hysterical in their 

 behaviour. Like the pegmatites of the Waindd, further to the south- 

 east and probably in an exposure of the same formation, those of Coorg 

 are remarkably free of accessory minerals. Garnets occur, but no trace 

 of schorl, which is so common in Bengal and Nellore, has been found. 

 The London brokers, noticing a few plates amongst the samples 

 striated and damaged, concluded that the defects were caused or 

 aggravated by blasting ; but unfortunately such is not the case : the 

 striations that I have examined all conform to the pressure-figure 

 (see p. 18) and must have been produced by the stresses suffered 

 during earth-movements. Consequently, precaution and care in mining 

 will not rid the mica of these defects, which must always contribute 

 ( 46 ) 



