M. A. Delesse's Researches on Granite. 



343 





SiO 3 . 



Al 2 3 . 



Fe 2 O 3 . 



CaO. 



Ko,NaO, 

 MgO. 



Loss by 

 burning 



Sum. 



I. 



70-8 



v 



s 



05 



124 



l'O 



100 



153 



II. 



68-5 



* 



1-3 





09 



... 



III. 



IV. 



673 



64*8 



16-1 | 1-9 



06 

 1-1 



133 

 12-7 



0-8 

 1-4 



100 



100 



200 



V. 



64-8 



211 



0-7 









VI. 



633 



20-2 



1-8 



11-8 



2-9 



100 



VII. 



638 



18-7 



23 



13-8 



1-4 



100 



The loss of silica is replaced by alumina and lime. These 

 variations depend very much (as I have proved elsewhere, 

 Bull, de la Soc. Geol., 2d Ser., vol. ix., p. 464) upon the posi- 

 tion in the mass, the more central and elevated being the 

 more siliceous, and upon the nature of the rocks, in junction. 



The second type of granite is the granite of the Vosges. I 

 group under this name the varieties which have been called 

 common granite, leptynite, and gneiss. 



Its essential minerals are quartz, orthose, feldspar of the 

 sixth system, two micas — a dark and a bright. 



The quartz is in grayish-white grains. The orthose is the 

 preponderating mineral ; it occurs in minute lamellae or 

 grains, the analysis of which gave — 



Silica, .... 





66-08 



Alumina and traces of peroxide of 



iron, 



18-70 



Oxide of manganese, 





trace. 



Lime, .... 





0-93 



Magnesia, 





0-45 



Soda, .... 





3-77 



Potash, .... 





9-11 



Sum, . . 99-04 



The large amount of silica is no doubt due to quartz me- 

 chanically mixed. 



Orthose and quartz are found in the most degraded varie- 

 ties of this granite. 



The dots indicate that the quantitative determination was not made. 



