

SOME CONCEPTIONS OF THE SOIL 



of soil almost always come directly from the original rock 

 as do particles of orthoclase, biotite, and apatite. Hematite, 

 the kaolinite group and the chlorite and epidote groups 

 generally originate in soils through weathering. The fol- 

 lowing list of minerals is by no means complete, yet it includes 

 the more important forms from the soil and plant standpoint. 



A LIST OF THE MOST IMPORTANT SOIL MINERALS. 1 

 (The elements in bold type are those necessary for plant nutrition.) 



3 H 2 



1 Below are some of the most important mineralogical investigations of 

 soil: McCaughey, W. G., and Williams, H. F., The Microscopic De- 

 termination of Soil-Forming Minerals; U. S. Dept. Agr., Bur. Soils, Bui. 

 91. 1913. Plummer, J. K., Petrography of Some North Carolina 

 Soils and Its Relationship to their Fertilizer Requirements, Jour. Agr. 

 Res., Vol. V, No. 13, pp. 569-581. 1915. Robinson, W. O., The Inor- 

 ganic Composition of Some Important American Soils; U. S. Dept. Agr., 

 Bui. 122. Aug., 1914. 



