90 



MINING INDUSTEY. 



Table of Quantitative Analyses of Rocks, by W . G. Mixter. 





Andesite. 



Propylite. 



Silica 



Alumina 



Ferric oxide 



Lime 



Magnesia - 



Potassa 



Soda 



Water 



59.22 



18.20 



6.69 



5.51 

 2.90 



1-39 

 3-31 

 2.80 



58.68 



17.90 



4. II 



5-87 

 2.03 



3-19 

 2.07 



6.53 



100.02 



100.36 



From these chemical data it is seen that the propylite, waters, and iron 

 pyrites, furnish all the materials for the chemical action now going on in the 

 vein. To the orthoclase of the propylite, with its large proportion of potassa, 

 may be traced the potash which is found so frequently in the waters and vein- 

 materials. 



The horses from various localities throughout the lode have been examined 

 for silica and were found to contain from 68 to 85 per cent. The quantitative 

 analysis of a propylite horse above given, represents a fair average of their 

 chemical composition. The comparison of the tenure of silica with that of 

 the propylite shows the important fact that all the vein-materials are more 

 highly charged with silicic acid than is the normal propylite wall-rock. When 

 it is considered that so basic a rock as the syenite forms the other wall, the 

 writer thinks the conclusion inevitable that the immense masses of quartz 

 cannot be the result of lateral secretion in situ. The horse materials, 

 especially, contained rather more silica than the normal propylite, and those 

 specimens which have been taken from the immediate east country, are 

 charged to their normal percentage with silica. Whence then is the enormous 

 volume of this mineral \ That it came from below, brought upward by the 

 ascending currents of hot water, there seems to be little doubt ; likewise that 

 it filled the fissured chambers with a uniform charge of quartz is evident from 

 their internal structure. The rocks upon either side in immediate contact with 

 the vein, and as far as we have seen in the eroded gorges of the syenite, and 



