8 



THE PRINCIPLES OF SOIL MANAGEMENT 



4. Relative abundance of the common minerals. 



Hall quotes D'Orbigny as saying that in the earth's 

 crust the chief minerals are present in the following 

 proportions: 



Feldspars 48 



Quartz 35 



Micas 8 



Talc 5 



Carbonate of lime and magnesium 1 



Hornblend, augite, etc 1 



All other minerals and weathered products 2 



100 

 These general relations agree with the statements 

 of Chamberlin and Salisbury, who give the following 

 summary of the salient facts relating to the composition 



of minerals: " (1) 

 Out of the sev- 

 enty-odd chemical 

 elements in the 

 earth, eight form 

 the chief part of 

 it. (2) One of 

 these elements 

 uniting with the 

 rest forms nine 

 leading oxides. (3) 

 One of these ox- 

 ides acts as an 

 acid, and the rest 

 as bases. (4) By 



.biG. 1. bection of granite, magnified. The . . 



crystals are orthoclase, microline, plagioclase, their Combination 



quartz, black mica or biotite, white mica or mus- . . 



covite. (Merrill.) they form a series 



