MINING PRACTICE. 



91 



patterns of sheet zinc, tin or iron, to include the largest possible area 

 of good mica ; they are then cut along the ruled lines with a pair of 

 ordinary garden shears, one handle of which is fixed to a log of wood 

 in the ground with the cutting plane vertical (see plate I). A special 

 form of cutting table is used for large thick sheets, too heavy for the 

 shears. The table, 2 to 3 feet square (see plate I and figs. 19 and 20) 

 is made of a 2 to 3-inch block of teak-wood, supported on firm legs 

 and faced with a half-inch plate of steel (c) , with the upper border made 

 slightly acute to act as a cutting edge against the long, curved knife 

 {b), also about half an inch thick, and hinged against the steel plate at 

 the corner of the table. 



S^CZ- 



»r 



Flo. 20. Siction through the cutting edge of table shown in Fig. ig. 



Scale, one-fifth. 



An important part of the dressing operations consists of splitting 

 the mica to remove damaged films or inclusions of foreign minerals 

 which would, if allowed to remain, reduce the market value of the 

 whole sheet, the slight loss of weight so incurred being more than com- 

 pensated for by the higher price obtained for the residue. It is this 

 part of the dressing which requires most judgment, and it is the part 

 too often neglected by the managers, who do not fully appreciate its 

 value. 



(3) Quality and Price. 



The mica sent to the market from India is practically all muscovite, 

 which varies greatly in colour. The characteristic and favourite 

 G ( 81 ) 



