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Chapter 2 continued

Chapter 2 continued. 2:1 phyllosilicates (Chlorites) Non-silicates. 2 Tetrahedral sheets. + 1 octahedral sheet. + 1 octahedral sheet (in the interlayer). http://pubpages.unh.edu/~harter/crystal.htm#2:1%20MINERALS. Form “2:1:1” minerals 1:1 mineral. 0.7 nm. 1.4 nm. Chlorite structure

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Chapter 2 continued

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  1. Chapter 2 continued 2:1 phyllosilicates (Chlorites) Non-silicates

  2. 2 Tetrahedral sheets + 1 octahedral sheet + 1 octahedral sheet (in the interlayer) http://pubpages.unh.edu/~harter/crystal.htm#2:1%20MINERALS

  3. Form “2:1:1” minerals 1:1 mineral 0.7 nm 1.4 nm

  4. Chlorite structure 2:1 interlayer interlayer Oct. Tet. Oct. 2:1 layer Tet. http://pubpages.unh.edu/~harter/crystal.htm

  5. 2:1 Interlayer or Chlorite Minerals (formerly called 2:1:1 or 2:2 Layer Silicates) 2:1 layer silicate with positively charged Al(OH)x (Dioctahedral) or Mg(OH)x (Trioctahedral) in the interlayer (x < 3) e.g., Al(OH)2+1 Properties: S.A. = 70-150 m2/g c-spacing = 1.4 nm Non-expansive CEC = 10-40 cmol/kg High pH-dependent charge

  6. http://www.geoclassroom.com/mineralogy/chlorite.GIF

  7. Crystal structure of chlorite http://www.gly.uga.edu/schroeder/geol6550/chlorite.gif http://www.soils.wisc.edu/courses/SS325/chlorite.gif

  8. http://www.uwm.edu/Course/422-100/Mineral_Rocks/chlorite1.jpghttp://www.uwm.edu/Course/422-100/Mineral_Rocks/chlorite1.jpg

  9. Chlorite hand specimen http://www.casdn.neu.edu/~geology/department/courses/minerals/ photogallery/index.html

  10. Non-Layer Silicates

  11. Allophane • Amorphous (non-detectable by X-Ray Diffraction) • Derived from volcanic ash in relatively young soils - the rapid cooling of lava ejected from volcanoes leads to deposition of much of the ash as amorphous glasses. Amorphous gels of silica, alumina, and silica-alumina polymers are formed during decomposition of the ash. • (Al2O3) (Fe2O3) SiO2 • Intermediate product of weathering • Highly pH dependent CEC = 5 - 350 cmol/kg • High S.A. = 70-300 m2/g

  12. Al, Fe, Mn, Ti Oxides, Hydroxides, and Oxyhydroxides • Weathering products of other minerals; Found in highly weathered soils Fe oxides impart soil color (brown, yellow, red, orange, black) • Often present as coatings on soil particles, in cracks, or as nodules High surface area Fe and Mn oxides indicate redox conditions pH dependent charge • See Table 2.5 Sparks p. 60 for list of common oxide minerals in soils

  13. Oxisol – high in Fe and Al oxides http://soils.usda.gov/technical/classification/orders/images/oxisol.jpg

  14. Microscopic view of an Inceptisol, showing small crystallites of carbonate minerals (around the central black void), quartz sand grains (white), and iron oxides and organic matter (dark brown). http://www.britannica.com/ebc/art/print?id=19571&articleTypeId=0

  15. csd.unl.edu

  16. http://fr.wikipedia.org/wiki/Structures_cristallines_des_oxydes,_oxy-hydroxydes_et_oxydes_de_ferhttp://fr.wikipedia.org/wiki/Structures_cristallines_des_oxydes,_oxy-hydroxydes_et_oxydes_de_fer

  17. Carbonates and Sulfate Minerals Calcite = CaCO3 Dolomite = CaMg(CO3)2 Siderite = FeCO3 Gypsum = CaSO4.2H2O Soluble minerals (compared to silicates) Present in arid zones (high evapotranspiration) Formed from precipitation out of solution as water evaporates

  18. Rosettes of gypsum

  19. Surface Area • Specific Surface = the surface area per unit weight of material (m2/kg) • Affects water retention and CEC • Total S.A. = External surfaces + Internal (interlayer) surfaces

  20. http://bio1151.nicerweb.com/doc/class/bio1151/Locked/media/ch06/06_07SurfaceVolumeRatio_L.jpghttp://bio1151.nicerweb.com/doc/class/bio1151/Locked/media/ch06/06_07SurfaceVolumeRatio_L.jpg

  21. http://www.gly.uga.edu/railsback/1121WeatheringArea.jpeg

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