Soil Science: An Overview of Non-Crystalline Minerals and Clay Minerals, Quizzes of Plant Taxonomy and Evolution

Download Soil Science: An Overview of Non-Crystalline Minerals and Clay Minerals and more Quizzes Plant Taxonomy and Evolution in PDF only on Docsity! TERM 1 Non- Crystalline Minerals DEFINITION 1 Allophane and Imogolite -colloid silicatesPoorly crystallizedMoste predominant in volcanic ash (andisols & spodosolsProperties charge varies with pH, adsorb OM, H20, PO4 TERM 2 Allophane and Imogolite DEFINITION 2 Colloide silicats TERM 3 Iron & Aluminum Oxide clays DEFINITION 3 Greater occurrence in highly weathered, utisols & oxisolsGeothiteHematitegibbsitecharge varies with pHlow stickyness and platicityStrong soil structure TERM 4 Geothite DEFINITION 4 FeOOH (yellowish brown) TERM 5 Hematite DEFINITION 5 Fe TERM 6 Gibbsite DEFINITION 6 Gibbsite, A3, is one of the mineral forms of aluminium hydroxide. It is often designated as -Al(OH)3 (but sometimes as -Al(OH)3.). TERM 7 Organic Soil Colloids DEFINITION 7 Functional group supply chargeMajority of charge from SOM quantitiy of charge depends on pH.Carboxy- R -COOH R- COOH + OH- = R-COO- + H2OPhenolic- sorry could not get it symbol to postEnolic-R-OH TERM 8 Cation Exchange Capacity DEFINITION 8 SumIn soil science, cation-exchange capacity or CEC is the number of exchangeable cations per dry weight that a soil is capable of holding, at a given pH value, and available for exchange with the soil water solution. TERM 9 Cation DEFINITION 9 Basic - Ca2+, Mg2+, Na+, K+Acidic- Al3+, H+ TERM 10 Importance of CEC DEFINITION 10 Nutrient retentionBuffering capacityAdsorption of heavy metals TERM 21 Mineralogical definition of clay mineral DEFINITION 21 Clay mineral is a layer silicate composed of Si- tetrahedral sheets and gibbsite [Al(OH30] or brucite [Mg3(OH6)] octehedral TERM 22 Kaolinite DEFINITION 22 Kaolinite is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O5(OH)4. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra. TERM 23 Properties of Kaolinite 1:1 DEFINITION 23 No interlayer spacesurface area 5-30 m2/g Hexogonal crystalsplasticity = lowshrink-swell =noneCEC=1- 15cmolc/kgdiameter .1-5um coarse clay - fine silt TERM 24 Pyrophyllite DEFINITION 24 No isormorphic subs Si8Al4O20(OH)4Pyrophyllite is a phyllosilicate mineral composed of aluminium silicate hydroxide: Al2Si4O12. It occurs in two more or less distinct varieties, namely, as crystalline folia and as compact masses; distinct crystals are not known. TERM 25 Smectites - montomorillonite DEFINITION 25 Most substitution is in octahedral layer(Si7.8Al.2) (Al3.4Mg.6)O20(OH)4 TERM 26 Properties of Smectite DEFINITION 26 Internal Surface = very highSurface area = ext. 80-150, int. 550-650 m^2/gPlasticity = highShrink-swell = highCEC =80 to 150 cmolc/kgDiameter .01- 1 um TERM 27 Properties of vermiculite DEFINITION 27 Internal surfave = highsurface area = ext. 70=120, int. 600- 700 m^2/gPlasticity = MeduimShrink-swell = mediumCEC =100-200 cmolc/ kgDiameter = .1 to 5 um TERM 28 Illite DEFINITION 28 Hydrous mica or fine grained micaK1.4(si6.4Al1.6)Al4O20(OH)4 TERM 29 Properties of Illite DEFINITION 29 Internal surface = noneSurface area=70-175 m^2/gPlasticity = medium "slightly"shrink - swell = non-expanding (minimal swelling)CEC = 10-40 cmolc/kgDiameter .2 um -2.0 um TERM 30 Clay Mineral Formation DEFINITION 30 Clay minerals formed by physical and chemical weathering or alteration of certain primary minerals.Ex. feldspar, micas, muscovite, biotite TERM 31 2:1 Vermicolite DEFINITION 31 Tritahedral (Si6Al2)(Mg5.4Fe^3 0.6) O20(OH)4Dioctahedral (Si7.2Al.8)(Al3.4Mg.6)O20(OH)4Substitutions in tetrahedral and OctahedralDioctahedral is more resistant to weatheringDioct>trioct TERM 32 Biotite DEFINITION 32 Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . K2(Si6Al2) (Mg,Fe)6O20(OH)4 TERM 33 Muscovite DEFINITION 33 Muscovite is a phyllosilicate mineral of aluminium and potassium with formula KAl2(AlSi3O10)(F,OH)2, or (KF)2(Al2O3)3(SiO2)6(H2O).