SOME GENERAL CONSIDERATIONS 



9 



following list will give some idea of the minerals normally 

 present in soils : — 



COMMON SOIL-FORMING MINERALS 



1. Quartz . . Si0 2 



2. Orthoclase K 2 . A1 2 3 . 6 Si0 2 



3. Plagioclase Na 2 . A1 2 3 . 6 Si0 2 , CaO . A1 2 3 . 2 Si0 2 



or combinations 



4. Hornblende Chiefly Ca(MgFe) 3 SiA 2 with 



Na 2 Al 2 Si 4 Oi 2 and (MgFe) 2 . (AlFe) 2 . 

 Si 2 0i 2 



5. Augite . . Chiefly CaMgSi 2 06 with 



(AlFe) 2 Si 2 6 



6. Muscovite 2 H 2 . K 2 . 3 A1 2 3 . 6 Si0 2 



(MgFe) 



7. Biotite . . 



8. Olivine . 



9. Serpentine 



10. Epidote . 



11. Apatite 



12. Zircon . . 



13. Chlorite . 



14. Calcite 



15. Dolomite . 



16. Gypsum 



17. Talc . . 



18. Hematite . 



19. Siderite 



20. Limonite . 



21. Kaolinite . 



22. Zeolites . 



(Si0 4 ); 



6SiO s 



(HK), (MgFe), (AlFe), 



2 (MgFe)O . Si0 2 



3 MgO . 2 Si0 2 . 2 H 2 



H 2 0.4Ca0.3(AlFe) 2 3 



3 Ca 3 P 2 8 + (CaFl 2 ) or (CaCl 2 ) or 



combinations 

 Zr0 2 . Si0 2 



H 40 (FeMg) 23 Ali4Sii 3 O90 

 CaC0 3 



CaC0 3 . MgC0 3 

 CaS0 4 . 2 H 2 

 H 2 0.3Mg0.4Si0 2 

 Fe 2 3 

 FeC0 3 



2 Fe 2 3 . 3 H 2 

 2 H 2 . A1 2 3 . 2 Si0 2 

 Complex hydrated aluminium silicates of 



Ca, K, and Na as Philolite (CaK 2 N 2 ) 



Al 2 Sii O 24 . 5 H 2 



