100 SOILS: PBOPEBTIES AND MANAGEMENT 



General Mineralogical Composition of the Sands and 

 Silts of Various Soil Provinces of the United States ^ 



Soil 



No or 

 Samples 



Minerals other than 

 Quartz in 





Sands 



Silts 



Residual 



Glacial and loessial . . 



Marine 



Arid 



12 

 6 



4 . 

 3 



35% 



12% 



5% 



37% 



21% 



15% 



8% 



42% 



It is to be seen immediately that in every case the 

 silt carries a larger quantity of the important soil-forming 

 minerals and a smaller quantity of quartz than does the 

 sand. This reveals at least one of the reasons for the 

 greater fertility and lasting qualities of fine-textured soils 

 as far as agricultural operations are concerned. It is 

 important to note, however, that, although quartz is 

 the predominating mineral in sands, all the common 

 soil-forming minerals are usually accessory. This merely 

 serves to again emphasize the fact that all soils contain 

 all the common minerals found in soil-forming rocks. 



It is also interesting to note the general differences 

 exhibited by the various soil provinces. The residual, 

 glacial, and coastal plain soils possess minerals other 

 than quartz in the order named. In the marine soils, 

 in particular, this difference has largely come about by 

 the disintegration and leaching that these soils have 

 undergone during their formation. The arid soils, due 

 to the suppression of chemical weathering and the activity 



^ McCaughey, W. G., and William, H. F. The Microseopie 

 Determination of Soil-Forming Minerals. XJ. S. D. A., Bur. 

 of Soils, BuL 91. 1913. 



