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 O . A1 2 3 . 6 SiO 2 



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



or combinations 



4. Hornblende Chiefly Ca(MgFe) 3 Si 4 Oi 2 with * 



Na 2 Al 2 SiA 2 and (MgFe) 2 . (AlFe) 2 . 

 Si 2 Oi 2 



5. Augite . . Chiefly CaMgSi 2 O 6 with (MgFe) 



(AlFe) 2 Si 2 O 6 



6. Muscovite 2 H 2 O . K 2 O . 3 A1 2 3 . 6 SiO 2 



ii in 



7. Biotite . . (HK) 2 (MgFe) 2 (AlFe) 2 (SiO 4 ) 3 



8. Olivine . 2 (MgFe)O . SiO 2 



9. Serpentine 3 MgO . 2 SiO 2 . 2 H 2 O 



10. Epidote . H 2 O . 4 CaO . 3 (AlFe) 2 O 3 . 6 Si0 2 



11. Apatite . 3 Ca 3 P 2 O 8 + (CaFl 2 ) or (CaCl 2 ) or 



combinations 



12. Zircon . . ZrO 2 . SiO 2 



13. Chlorite . H 4 o(FeMg) 23 Al 14 Sii 3 O9o 



14. Calcite . CaCO 3 



15. Dolomite . CaCO 3 . MgCO 3 



16. Gypsum . CaSO 4 .2H 2 O 



17. Talc . . H 2 0.3MgO.4SiO 2 



18. Hematite . Fe 2 O 3 



19. Siderite . FeCO 3 



20. Limonite . 2 Fe 2 O 3 . 3 H 2 O 



21. Kaolinite . 2 H 2 O . A1 2 O 3 . 2 Si0 2 



22. Zeolites . Complex hydrated aluminium silicates of 



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

 Al 2 Sii O 24 . 5 H 2 O 



