17. Classification of some igneous rocks in relation to mineralogical composition and rock texture. Rock Texture Light-colored Minerals Dark-colored Minerals Feldspars, muscovite Quartz Hornblende, augite, biotite Coarse Granite Diorite Gabbro Peridotite/ Horblendite Inter-mediate Rhyolite Andesite Basalt Fine Felsite/Obsidian Basalt glass
18. Some of the More Important Sedimentary and Metamorphic Rocks and the Dominant Minerals Dominant Mineral Sedimentary Metamorphic Calcite CaCO 3 Dolomite CaCO 3 .MgCO 3 Quartz SiO 2 Clays Variable Variable Limestone Dolomite Sandstone Shale Conglomerate Marble Marble Quartzite Slate Gneiss Schist
19. The More Important Minerals Found in Soils Listed in Order of Decreasing Resistance to Weathering (1) Primary Minerals Secondary Minerals Quartz SiO 2 Muscovite K Al 3 Si 3 O 10 (OH) 2 Microcline K AlSi 3 O 8 Orthoclase K AlSi 3 O 8 Goethite Fe OOH Hematite Fe 2 O 3 Gibbsite Al 2 O 3 .3H 2 O Clay minerals (Al silicates)
20. The More Important Minerals Found in Soils Listed in Order of Decreasing Resistance to Weathering (2) Primary Minerals Secondary Minerals Biotite K Al( Mg,Fe ) 3 (AlSiO 3 O 10 )(OH) 2 Albite NaAlSi 3 O 8 Hornblende Ca 2 Al 2 Mg 2 Fe 3 Si 6 O 22 (OH) 2 Augite Ca 2 (Al, Fe) 4 ( MgFe ) 4 Si 6 O 24 Anorthite Ca Al 2 Si 2 O 8 Olivine ( Mg,Fe ) 2 SiO 4 Dolomite ( Ca CO 3 . Mg CO 3 ) Calcite ( Ca CO 3 ) Gypsum ( CaS O 4 .2H 2 O)
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29. Origin of residual materials and soil texture Origin Texture Basalt, andesite, volcanic tuff Clayey soils Granite, coarse sandstones Loamy and sandy Siltstones, fine-grained sandstones Silt loam and silty clay loam textures
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39. n - sodium accumulation p - plowing - only used with A q - silica accumulation - very weathered or old soil r - soft rock - used with C or Cr s – an accumulation of illuvial iron t – accumulation of illuvial clay w - color or structure development (Bw) x - Fragipan - hard, dense layer that developed with time y - gypsum accumulation (CaSO 4 ) z – accumulation of soluble salts Lowercase letter symbols (cont’d).
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83. Soil Colors and Soil Attributes Soil Color Soil Attributes Brown to black (surface horizon) Accumulation of OM, humus Black (subsoil) Accumulation of Mn Parent material (e.g. basalt) Yellow to reddish Fe 3+ Well-aerated soils
84. Soil Colors and Soil Attributes Soil Color Soil Attributes Gray, bluish-green Fe 2+ Poorly drained soils White to gray Accumulation of salts White to gray Parent material: marl, quartz
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