FANR 3060: ROCKS
33 Cards in this Set
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Granite
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Light-colored igneous rock: 15-35% quartz, 30-45% feldspar, <30% ferromagnesian minerals
Coarse-grained, intrusive rock
Quartz + feldspar + Mica
Common intrusions in Piedmont
Weathers slowly to sandy/ clayey soils
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Rhyolite
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Light-colored igneous rock: 15-35% quartz, 30-45% feldspar, <30% ferromagnesian minerals
Fine-grained, extrusive (volcanic) rock
Similar composition to granite
Common in Western U.S.
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Diorite
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Intermediate colored igneous rock: 5-10% quartz, 30-40% feldspar, 40-50% ferromagnesian mineral
Coarse-grained, intrusive (plutonic)
Intermediate between granite and gabbro
Scattered intrusions occur in Piedmont
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Andesite
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Intermediate colored igneous rock: 5-10% quartz, 30-40% feldspar, 40-50% ferromagnesian mineral
Fine-grained, volcanic rock (extrusive)
Composition between rhyolite and basalt
Little in GA; common in Western U.S.
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Gabbro
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Dark colored igneous rock: <5% quartz, 25-40% feldspar, 60-75% ferromagnesian minerals
Dark colored, coarse-grained intrusive
Occurs as scattered bodies in Piedmont
Weathers to very clayey, red soils (high Fe)
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Basalt
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Dark colored igneous rock: <5% quartz, 25-40% feldspar, 60-75% ferromagnesian minerals
Dark- colored, high Fe extrusive (volcanic)
Common seafloor rock; rare in GA
Forms clayey red soils similar to gabbro
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Slate (Phyllite)
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Metamorphic Rock
Grey to black to reddish or yellow; dense, hard
Strongly foliated, often readily flakes into sheets
Parent rock: shale, siltstone; clay minerals common
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Quartzite
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Metamorphic Rock
Whitish to grey to brown; v. hard, brittle
Sandy texture, strongly cemented (largely quartz)
Massive; little foliation
Parent rock: sandstone
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Marble
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Metamorphic Rock
Bright white to greyish; mod. hard; smooth feel, luster
May fizz in acid fractures
Parent rock: limestone (mostly CaCO3)
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Schist
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Metamorphic Rock
Strongly foliated in thin, oriented sheet, often crumpled
Dark grey to black to silvery; Often micaceous layers
Parent rock: shales, conglomerates, ryholites, basalts
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Gneiss
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Metamorphic Rock
Alternating bands of light-colored, granular rock (quartz, feldspar) with thinner, foliated dark bands (mica, ferromagnesian)
Overall light color- whitish to tan to grey, darker bands
Parent rock: granites, diorites, shales, sandstones
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Amphibolite
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Metamorphic Rock
Even-grained, occasionally foliated, dark, hard, brittle
Dark green to grey to black: overall dark color
Parent rocks: gabbros, basalts, diorites
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Shale (Mudstone)
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Sedimentary Rock
Deposited Soil-like Materials (detrital)
Grey to brown to red; fairly soft, fine-grained, strongly laminated, easily flaked
Contains clay minerals, silts; may be fossiliferous
Erodes readily
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Sandstone
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Sedimentary Rock
Deposited Soil-like Materials (detrital)
Variable color, hardness; sandy texture (feel)
Massive, or may be bedded (banded)
Resists erosion, often forms ridges or bluffs
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Conglomerate
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Sedimentary Rock
Deposited Soil-like Materials (detrital)
Cemented mixture of coarse and fine sediments from sands to boulders
Usually resistant to weathering, erosion
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Limestone
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Sedimentary Rock
Precipitated or Organic Materials
Dense, even-grained, white to grey; may be thinly bedded, often fossiliferous; fizzes in acid
Mostly calcite, with clay, quartz impurities
Often bedded with shales; weathers rapidly
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Dolomite
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Sedimentary Rock
Precipitated or Organic Materials
V. similar appearance to limestone; fizzes weakly in acid; never fossiliferous
(Mg, Ca) CO3: partial replacement of Ca by Mg
More resistant to weathering, erosion than limestone
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Coal
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Sedimentary Rock
Precipitated or Organic Materials
Black, vitreous, soft, often fossiliferous
Compacted/heated plant remains from peat deposits of the Carboniferous period
Occurs in seams with shales, sandstones
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Quartz
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Light colored primary mineral (primarily Al and Si, some K and Ca)
Whitish to colorless; irregular cleavage
SiO2; no nutrient value
Very resistant to weathering
Common in granites and gneisses
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Orthoclase
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Light colored primary mineral (primarily Al and Si, some K and Ca)
Feldspar Group
Whitish to grey to tan; strong 90 degree cleavage
Aluminosilicates (Si + Al) with Ca, K, Na
Very common rock-forming minerals
Weather fairly easily in soils to form clay
Clear crystal faces
K-containi…
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Plagioclase
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Light colored primary mineral (primarily Al and Si, some K and Ca)
Feldspar Group
Right angle cleavage; striations (fine lines) on crystal faces
Ca and /or Na aluminosilicate
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Hornblende
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Dark colored primary mineral (higher in Fe and Mg, with Ca)
Ferromagnesian group
Dark-colored (black to dark greenish); metallic luster
Strong cleavages
aluminosilicates with Fe, Mg and some Ca, Na, K
Weather rapidly to form Fe oxides and clay minerals
Diamond-shaped cleavage (56 de…
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Augite
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Dark colored primary mineral (higher in Fe and Mg, with Ca)
Ferromagnesian group
Right- angle (90 degree) cleavage
Occurs in many igneous rocks, esp. dark-colored ones (gabbros, diorites, etc.)
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Mica Group
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Distinctive platy morphology (flaky sheets)
Common in igneous and metamorphic rocks
Aluminosilicates with K or Fe + Mg
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Muscovite
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Dark colored primary mineral (higher in Fe and Mg, with Ca)
Mica group
Transparent, shiny plates
K-containing aluminosilicate
Common in granites, Shists
Weathers slowly in soils into clay
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Biotite
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Dark colored primary mineral (higher in Fe and Mg, with Ca)
Mica group
Black, shiny plates
Fe + Mg cause dark color
Accessory mineral in many rocks
Weathers rapidly to form clays, Fe oxides
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Calcite
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Evaporite Mineral:
White to grey to colorless; hexagonal crystals, often microscopic; fizzes with acid addition
CaCO3; major component of limestone rock
Chemical precipitate, or biological (fossiliforeous)
weathers rapidly in humid region soils
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Gypsum
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Evaporite Mineral:
White, color-less, grey; flat prismatic crystals, often microscopic; low density, soft mineral
CaSO4; soluble in water, occurs only in acid region soils, geologic deposits (salt domes)
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Rock Salt (Halite)
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Evaporite Mineral:
Soft, colorless to grey, perfect 90 degree cleavage (cubic)
NaCl; very soluble in water, salty taste
Found geologically; in soild, only in acid regions
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Kaolinite
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Secondary mineral--> clay mineral
Soft, platy (microscopic) aluminosilicate
Fine-grained, whitish to grey microscopic platy crystals; related to micas; aluminosilicates
Mineral group; includes kaolin and vermiculite
Very important components of fine fraction of soils (give soil water …
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Vermiculite
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Secondary mineral--> clay mineral
Soft, platy aluminosilicate; larger crystals
Weathering product from micas; occasional in GA
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Hematite
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Secondary mineral--> clay mineral-->Fe oxides
Red to Yellow to greyish to black, dense; fibrous or platy crystals rare- usually fine or massive
Weathering products- precipitate from Fe
Released by primary mineral weathering
Red to lustrous black, dense; Fe2O3
Common Fe mineral in wel…
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Geothite
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Secondary mineral--> clay mineral-->Fe oxides
Yellow to brownish; dense, FeOOH
Common brownish pigment in wtter soils
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FANR 3060: ROCKS