The unconsolidated mineral and organic matter on the surface of the earth that has been subjected to and shows effects of genetic and environmental factors of: 1) climate; 2) macro- and microorganisms, conditioned by 3) relief, acting on
Metamorphic – recrystallized in the solid state from heat and pressure.
Sedimentary – formed from particles of other rocks or from solution.
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
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
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)
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)
Leaching out; lighter in color than horizons above or below
B - below an A, E, or O with an accumulation of clay, iron,
humus or carbonates (CaCO 3 ); zones of illuviation
- or alteration of the original parent material, development of
color or structure
C - little affected by pedogenic processes and lack properties
of O-A-B-E; the Parent Material
R - hard rock
Lowercase letter symbols to designate subordinate distinction within master horizons.
a - organic matter - highly decomposed
b - buried soil horizon
e - hemic - mod. decomp. - organic soil
f - frozen soil - permanently frozen, permafrost
g - gleyed soil - gray color due to low O2 - reduction
h - accumulation of illuvial humus
i - slightly decomposed organic matter
k - accumulation of calcium carbonate (CaCO3)
m – an indurated layer, or hardpan, due to silicaion or
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).
Value is expressed as the numerator of the fraction.
Chroma is along the bottom, and is the denominator of the fraction.
Chroma is the relative purity or strength of the color, low chromas have dull colors, while high chromas have bright colors.
Example: A color of 10YR 3/2 has a hue of
10YR , a value of 3 , and a chroma of 2 .
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
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