1. Soil Mineralogy and Chemistry Lecture 4

2. Phyllosilicate Minerals

3. Building of Tetrahedral Sheets * Linked SiO 4 tetrahedra

4. SiO 4 Tetrahedron

5. Polyhedral View

6. x y z

7. Si 6 O 18

8. Polyhedral View

9. Si 6 O 18 Spaced Filled View

10. Linking Rings to Form Tetrahedral Sheets

11. Tetrahedral Sheet Si:O 2:5 4.11

12. Tetrahedral Sheet unsaturated ‘edge’sites 4.12

13. Tetrahedral Sheet unsaturated apical oxygens 4.13

14. Building of Octahedral Sheets

15. Al(OH) 6 or Mg (OH) 6 Octahedra OH

16. Al(OH) 6 or Mg (OH) 6 Octahedra

18. Octahedral Sheet OH 4.18

19. (tri)Octahedral Sheet Mg (OH) 6 Octahedra 4.19

20. Dioctahedral Sheet Al(OH) 6 Octahedra 4.20

21. A Georgian Ultisol

22. Octahedral-Tetrahedral Linkage

23. Sharing of Apical Oxygens in Tetrahdral Sheet with Hydroxyls of Octahedral Sheet Serpentine (1:1 trioctahedral mineral) tet oct 4.23

24. Sharing of Apical Oxygens in Tetrahdral Sheet with Hydroxyls of Two Octahedral Sheets tet oct tet Talc (2:1 trioctahedral mineral) 4.24

25. Tet Oct Tet

26. tet oct Short hand, Block notation Short-hand Symbols 4.26

27. Isomorphic Substitution  permanent (layer) charge

28. Al 3+, Fe 3+ Si 4+ tet oct Mg 2+ Al 3+ Isomorphic Substitution 4.28

29. Terminal Bonds  pH-dependent charge

30. terminal bonds Terminal Bonds 4.30

31. tet oct tet oct tet oct tet oct tet oct trioctahedraldioctahedral octahedra 1:1 2:1 T:O (class) brucite gibbsite serpentine kaolinite pyrophyllite talc Phyllosilicates, NO layer charge 4.31

32. tet oct tet oct tet K+K+ K+K+ K+K+ Phyllosilicates: 2:1 with layer charge micas 1 unit of (-) layer charge per formula unit tet oct tet oct tet K+K+ H2OH2O Ca 2+ H2OH2O H2OH2O < 1 unit of (-) layer charge per formula unit 2:1 clay minerals 4.32

33. 4.33

34. 4.34 Structure d-spacing Interlayer Status: d-spacing (and mica) K+K+

35. CEC cmol/Kg Properties of Clay Minerals 4.35

36. Western GA Ultisol Kaolin and Oxide Rich Soil Accessory Minerals 4.36

37. Young, weakly weathered soils = fine-grained mica, chlorite, vermiculite (Entisol, Inceptisol) Intermediate weathering = vermiculite, smectite, kaolinite (Mollisol, Alfisol, Ultisol) Strong weathering = kaolinite, hydrous oxides (Ultisol--> Oxisol) Clay mineralogy reflects weathering processes 4.37

38. Smectite Soil NE Montana Vertisol Hawaiian Oxisol Iron and Al-oxide Rich 4.38 ?

39. 4.39

40. Organic Matter 4.40 - reactive functional groups: carboxyl, hydroxyl, phenolic * Humus, Humic Acid, Fulvic Acid