GEOGRAPHICAL DISTRIBUTION. 57 



seriously to the proportion of waste. Notwithstanding the common 

 opinion to the contrary, the mere shock of blasting does not generally 

 injure mica. 



There are some very interesting features in the Coorg pegmatites 

 showing that earth-movement, occurring during the time when the 

 pegmatites are consolidating, may give rise to phenomena often mis- 

 taken for subsequent crushing of the solid rocks. Fig. 14 represents 

 a section through a specimen composed of muscovite and quartz. 

 The former mineral is in a well-defined crystal which has been faulted 

 out along its basal cleavage-surfaces like a pack of cards, but is 

 otherwise undamaged. The quartz, when examined by the micros- 

 cope in polarised light, is found to be in the form of very minute granules 

 which are independent crystals, and the granular portions form tongue- 



FiO. 14. Faulted crystal of muscovite in quartz granulated by movement 

 during crystallization. 



like, sugary-looking streaks between clearer layers which are crys- 

 tallized on ia larger scale. From a sample of the quartz alone one 

 would naturally suppose that the mineral had at one time been all as 

 clear and transparent as the glassy patches, and that the sugary 

 structure of the white tongues had been produced by crushing. But the 

 mica, which, compared with quartz, is a very delicate mineral, would 

 never have been preserved so little damaged if the crushing had occurred 

 when the quartz was solid. Now it is certain, from the fact that the 

 mica crystals have their crystal outlines perfectly developed, that the 



< 47 ) 



