Common Rocks and Minerals in Soil Parent Materials

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Common Rocks and Minerals in Soil Parent Materials

• Laboratory 2

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Objectives of the Lab

• Know the definition of a mineral and a rock.
• Recognize common minerals and rocks.
• Understand the general geology of North Carolina

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Minerals

• Minerals are naturally occurring homogenous
  solids that were inorganically formed, having a
  definite chemical composition, and an orderly
  atomic arrangement.
• Most minerals have fairly definite physical
  properties such as crystal form, color, luster,
  hardness, specific gravity, and solubility.
• Minerals are classified as to their origin and
  chemical composition.

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Types of Minerals

• Based on origin, minerals may be primary or
  secondary minerals.
• Primary minerals are formed when molten rock
  cools and solidifies.
• Secondary minerals are formed by the weathering
  of primary minerals.

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Primary Minerals

• -Formed directly from molten rock

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Quartz Si02

• Most common soil forming mineral
• Make up 13 of earth's crust and from 30 to 40
  of the average soil
• Commonly a translucent milky-white color
• Hard enough to scratch glass
• Resistant to weathering
• Present in granite absent from basalt
• Does not contribute plant nutrients to the soil

http//www.luc.edu/faculty/spavko1/minerals/quartz
/qa1.htm
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Orthoclase Feldspar KAl1Si3O8

• Slightly harder than glass
• Commonly white, orange, or pink in color
• Fine wavy lines may occur within crystals
• Flat surfaces are common (intersecting at 88-90
  angles)
• The most abundant mineral in granite
• Is an important source of potassium

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Plagioclase Feldspar

• Slightly harder than glass
• Common gray color (from almost white to dark
  bluish gray)
• Commonly has striations (flat faces within
  crystals seen as straight lines on surface)
• Flat surfaces are common (interesting at 87-89
  angles)
• Weathers more readily than orthoclase

http//www2.nature.nps.gov/GEOLOGY/usgsnps/rxmin/m
ineral.html
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Horneblende

• Slightly harder than glass
• Black, dark brown, or dark green in color
• One of the dark-colored minerals in granite
• Weathers more rapidly than feldspar, but persist
  in soils as dark colored gravel

http//cmsc.minotstateu.edu/Labs/web20minerals/Ho
rnblende.html
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Muscovite

• Easily spilt into thin flexible elastic plates
• Has shiny surface
• Present in granite, basalt, loess, and glacial
  till
• Is the Al mica and is colorless
• Contains more potassium than Biotite

http//www.cropsoil.uga.edu/soilsandhydrology/imag
es/Muscovite.jpg
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Biotite

• Easily spilt into thin flexible elastic plates
• Has shiny surface
• Present in granite, basalt, loess, and glacial
  till
• Is the Mg, Fe mica and is black
• Has more iron and magnesium

http//www.pitt.edu/cejones/GeoImages/1Minerals/1
IgneousMineralz/Micas/BiotiteFlakes.JPG
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Secondary Minerals

• -Formed from primary minerals

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Gypsum - CaSO4 2H2O

• Forms from evaporating calcium sulfate-bearing
  waters
• Very soft and weathers fairly readily
• Accumulate in large quantities in semi-arid
  regions
• Can be both a primary and secondary mineral

http//dave.ucsc.edu/myrtreia/photos/gypsum.jpg
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Calcite CaCO3

• Commonly found in limestone and Marble
• Much softer than glass harder than fingernails
• White or colored by impurities
• Slightly soluble in water
• Effervesces in dilute HCI (release bubbles of
  CO2)

http//www.beg.utexas.edu/mainweb/publications/gra
phics/calcite400.jpg
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Dolomite - CaCO3 MgCO3

• Most common liming material in NC
• Similar to calcite
• Contains Mg

http//hyperphysics.phy-astr.gsu.edu/hbase/mineral
s/imgmin/dolomite.jpg
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Iron Oxides

• Formed through chemical weathering
• Geothite (FeOOH) gives yellow color in soils
• Hematite (Fe2O3) responsible for red coloration
  in soils

http//www.uwrf.edu/wc01/mont-goet1.JPG
http//www.cst.cmich.edu/users/dietr1rv/hematite-b
.JPG
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Clay Minerals

• Highly colloidal
• Formed primarily form chemical weathering of
  primary minerals
• Ability to adsorb or hold nutrient ions on their
  surfaces

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Rocks

• Rocks are combinations of two or more minerals.
• There are three major groups of rocks igneous,
  metamorphic, and sedimentary.

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The Rock Cycle
http//rst.gsfc.nasa.gov/Sect2/rock_cycle_800x609.
jpg
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Igneous Rocks

• Formed when molten rock cools and solidifies.
• This is the most abundant group of rocks within
  the earth's crust.
• Classified on the basis of their chemical
  composition
• Acidic (Felsic)
• Usually light colored
• Basic (Mafic)
• Igneous rocks that have less than 50 SiO2
• Neutral
• Igneous rocks that have between 50 and 65 SiO2

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Intrusive Igneous Rocks

• Rocks deep within the earth's crust were formed
  by relatively slow cooling process.
• Have coarse-grained (pea size) texture.
• Intrusive mode of occurrence.

http//epswww.unm.edu/facstaff/zsharp/103/Lecture
207,20rocks_files/image004.gif
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Extrusive Igneous Rocks

• At or near the earth's surface the igneous rocks
  developed by rapid to very rapid cooling
  processes.
• They have fine grained (size of sugar crystals)
  or glassy textures.
• These are termed as extrusive in mode occurrence.

http//epswww.unm.edu/facstaff/zsharp/103/Lecture
207,20rocks_files/image004.gif
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Examples of Igneous Rocks

• -Formed from molten rocks

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Granite

• Are coarse-grained and light colored
• has quartz and orthoclase feldspar as principal
  minerals
• Acidic in chemical composition and intrusive in
  mode of occurrence

http//www.beg.utexas.edu/mainweb/publications/gra
phics/granite.htm
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Syenite

• Relatively coarse-grained
• Contains large amounts of feldspar and hornblende
  
• Classified as neutral and intrusive

http//www.guilford.edu/geology/imagelibrary/MVC-0
80F.JPG
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Rhyolite

• Mineralogical and chemical composition are
  similar to granite
• Fine grained in texture
• It is acidic in chemical composition
• Extrusive in mode of occurrence

http//volcano.und.edu/vwdocs/vwlessons/rocks_pics
/rhyolite.jpg
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Gabbro

• Dark colored
• Has a predominance of plagioclase feldspar,
  hornblende, and augite
• Basic
• Intrusive
• Coarse-grained

http//www.geo.umn.edu/mgs/virt_egg/gabbro.jpg
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Basalt

• Same chemical and mineralogical composition as
  gabbro
• Fine-grained
• Basic in chemical composition
• Extrusive in mode of occurrence

http//itc.gsw.edu/faculty/tweiland/basalt.jpg
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Obsidian

• Is volcanic glass
• Dark colored
• Acidic in chemical composition
• All volcanic rocks are extrusive in mode of
  occurrence

http//www.drexel.edu/coe/enggeo/rocks1/obsidian.J
PG
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Sedimentary Rocks

• Result from the erosion and deposition of
  sediments
• Have two classifications clastics or
  precipitates.

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Clastic Sedimentary Rocks

• Are sedimentary rocks which have been formed
  through physical or mechanical means.
• Vary in size.
• Cementing agents may be clay, iron oxide, silica,
  or calcium carbonate.

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Precipitate Sedimentary Rocks

• Types of sedimentary rocks that have been
  produced by chemical or biochemical precipitation
  of ions from solution (biochemical precipitates
  usually involve marine animals and may be
  fossiliferous).

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Examples of Sedimentary Rocks

• -Formed from erosion and deposition of sediments

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Conglomerates

• Formed from rounded pebbles or boulders (gt2mm in
  diameter)
• Cemented together with finer-grained material
• Weather to a very coarse material-which-may forma
  gravelly soft

http//comp.uark.edu/sboss/rockbag35.jpg
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Sandstone

• Consists of sand grains (0.5 to 2mm in diameter)
• Gives rise to sandy or sandy loam soil

http//www.beg.utexas.edu/mainweb/publications/gra
phics/sandstone400.jpg
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Shale

• Composed of minute particles (lt0.005mm diameter)
  which are consolidated
• Predominant mineral is clay which is deposited in
  slowly moving water
• Soils derived by shales are clayey

http//csmres.jmu.edu/geollab/fichter/SedRx/rkimag
es/shale2-899.jpg
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Limestone

• Usually fine-grained chemical precipitates.
• Principal minerals are Calcite and dolomite
• Durng weathering the carbonate minerals dissolve
  and leach away
• Remaining impurities determine the nature of the
  developed soil

http//www.dep.state.fl.us/geology/geologictopics/
rocks/miami_limestone.jpg
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Metamorphic Rocks

• Form from igneous and sedimentary rocks exposed
  to extreme heat and/or pressure
• These are classified according to their structure
  and parent material, either as banded (foliated)
  or non-banded.

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Banded (Foliated) vs. Non-banded Metamorphic Rock

• Banded metamorphic rocks have more or less
  parallel layers of different minerals and are
  usually uniformed in color or they alternate
  light and dark-colored layers.
• Non-banded metamorphic rocks have a random
  pattern of mineral crystals.

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Examples of Metamorphic Rock

• -Formed from parent rock due to heat and/or
  pressure

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Gneiss

• Banded (alternates light and dark bands)
• Derived primarily from acidic igneous rocks.
• Contains an abundance of feldspar

http//www.beg.utexas.edu/mainweb/publications/gra
phics/gneiss400.jpg
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Schist

• Layered
• Fairly uniform in color
• These are metamorphosed shale, gneiss, or basic
  igneous rock.
• Newly formed minerals like mica, chlorite, and
  hornblende tend to predominate

http//ocw.mit.edu/ans7870/12/12.108/f04/imagegall
ery/lab2/images/lab2-5.jpg
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Slate

• Layered
• Derived from shale
• Mineral grains are invisible
• Is more dense and compact than shale and cleaves
  into sheet

http//www.es.ucl.ac.uk/schools/Glossary/slate.jpg
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Quartzite

• Non-layered metamorphosed sandstone
• Very hard
• Weathers extremely slowly
• The rock fractures through sand grains which are
  mainly quartz

http//www.es.ucl.ac.uk/schools/Glossary/quartzite
.jpg
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Marble

• Is a recrystallized limestone with a random array
  of mineral grains
• Coarser-grained than parent limestone
• Weather more slowly than limestone
• The impurities determine the kind of soil.

http//www.drexel.edu/coe/enggeo/rocks2/marble.JPG
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Physiographic Regions of NC

• There are 3 physiographic regions in North
  Carolina Coastal Plain, Piedmont, and Mountain
  region.
• In North Carolina, all 3 rock types are present.

http//nc.water.usgs.gov/projects/icons/Physio.gif
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Coastal Plain Soils

• Coastal Plain soils are formed from weathered and
  eroded rock particles that are moved by water and
  may be alluvial or marine sediments (sedimentary
  rock).
• These sediments have similar minerals, so parent
  material differences are related to changes in
  the amounts of sand, silt, and clay.
• Properties of parent materials within the same
  landform vary if changes in texture occur.

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Piedmont Mountain Soils

• The piedmont region consists of remnant
  metamorphic mountains with some sedimentary rock.
• The mountain region contains metamorphic rock
  with some igneous intrusions.

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Questions??