Term
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Definition
Ash
Fragmental/Clastic
Unlithified pyroclastic fragments having a grain size of less than 2.0mm |
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Term
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Definition
Granite
Random Crystalline
Phaneritic
Contains Quartz and Orthoclase
Only granite and rhyolite can have pink orthoclase
(others may contain plagioclase, biotite, horneblende) |
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Term
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Definition
Lapillistone
Clastic
Lithified
2.0-64.0 mm
Note: The things in the rock have no geometry. |
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Term
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Definition
Basalt
Random Crystalline
Aphanitic
porphyritic
Olivine Phenocrysts
Note: Olivine phenocrysts usually have no geometry |
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Term
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Definition
Mafite
No visible olivine phenocrysts
aphanitic
non-porphyritic
dark
Volcanic(extrusive)
Random crystalline |
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Term
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Definition
Pyroxenite
Phaneritic (coarse grained)
No quartz
>80% Dark
greenish black color suspects augite or horneblende
cleavage-2d at right angles
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Term
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Definition
Lapilli
Fragmental (clastic)
Unlithified
2.0-64.0 mm
Note: The finer grain component is ash |
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Term
Igneous
[image]
[image]
[image] |
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Definition
Andesite
Random Crystalline
Aphanitic (fine grained)
prophyritic
If dark crystals
dark crystals (horneblende)
Note: phenocrysts have geometry; not only do they exhibit crystal faces, cleavage surfaces are also obvious.
If light crystals:
light crystals (plagioclase)
Note: phenocrysts have geometry, like little shoeboxes. Some crystals have cleavage. |
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Term
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Definition
Horneblendite
Random Crystallilne
(predominently)Horneblende
Phaneritic
>80% Dark
>50% Horneblende
Shiny black cleavage
2-d not at right angles |
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Term
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Definition
Diorite
Crystalline
phaneritic
50-80% dark
No Quartz |
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Term
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Definition
Scoria
Highly Vesicular >50%
glassy
usually reddish
does not float |
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Term
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Definition
Gabbro
Random crystalline
Plutonic (intrusive)
phaneritic
no quartz
>80% dark
>50% plagioclase
look for striations or bluish irridescence |
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Term
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Definition
Obsidian
Felsic
glassy - looks like glass
non-vesicular
conchoidal fracture
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Term
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Definition
Rhyolite
crystalline
aphanitic
porphyritic
quartz phenocrysts
Note: use microscope - quartz crystals usually have no geometry but are easy to identify. |
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Term
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Definition
Pumice
extrusive volcanic rock
Low Density
High Silica content
Will Float
>50% vesicular
usually whitish
lapilli |
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Term
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Definition
Tuff
Clastic
fragmental
lithified (is formed into a rock)
grain size less than 2.0mm |
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Term
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Definition
Granodiorite
Random crystalline
phaneritic
has quartz in it
<50% dark |
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Term
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Definition
Dunite
Random crystalline
plutonic
phaneritic
no quartz
>80% dark
>50% olivine |
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Term
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Definition
Conglomerate
Clastic
Lithified, round clasts having a diameter greater than 2.0mm.
Chert/jasper/quarts clasts with calcite cement.
<p>Beware, the rock contains calcite only as a cementing agent. Do not mistake it for limestone
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Term
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Definition
Coqina
Dominant Mineral: Calcite
Granola Bar
Loosely compacted and lithified fossil hash.
Generally comprised of angular clasts greater than 2.0mm in diameter, but it is not a breccia. Remember it is a chemical ppt because the individual clasts are chemical ppt. |
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Term
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Definition
Oolitic Limestone
Oolites
Looks like sandstone. Remember the microscope if your best friend. Microscopic examination will reveal the presence of oolites. Oolites are spherical/highly rounded sand-size grains that are made of concentric rings (spheres) of calcite. |
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Term
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Definition
Breccia
Rubble >2.0mm
Lithified, angular clasts having a diameter greater than 2.0mm. Notice the very angular nature of the clasts. |
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Term
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Definition
Quartz Sandstone
100% quartz
Clastic
Lithified clasts having a diamter of 1/16 to 2.0mm.
Wind blown sands are usually fine grained sands nearing 1/16mm, and have frosted (not polished) surfaces. |
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Term
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Definition
Micrite
Very fine grained crystalline calcite. Rock usually exhibits conchoidal fracture
Looks like hardened silly putty
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Term
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Definition
Chert
Very fine grain gray to white crystalline quartz.
Easy to identify the quartz because it is the only common chemical ppt (sedimentary mineral) that is hard. |
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Term
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Definition
Sand
Unlithified clasts/grain size between 1/16 and 2.0mm.
Use a microscope to identify several minerals including quartz and calcite. Note the especially shiny, polished nature of the quartz clasts. |
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Term
Sedimentary
[image]
[image] |
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Definition
Fossiliferous Limestone
Greater than 50% calcite.
Presence of abundant fossils makes it easily identified.
3-D Non-90° |
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Term
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Definition
Chalk
Looks like chalk, looks like kaolinite, but reacts with HCl. Comprised of microscopic tests (Like shells) for single celled plants and animals.
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Term
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Definition
Arkose
Clastic
Granitic Mineralogy
Sand-sized grains
Lithified clasts 1/16-2.0mm makes it a sandstone.
Look closely to observe quartz and pink orthoclase, which are the essential minerals in the identification of granite. Comes from the weathering of grantie-terrain. Note the angularity of the grains. It implies the grains have been subjected to little transportation.
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Term
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Definition
Siltstone
Clastic
Note the gritty feel, but individual grains are invisible. Grains are <1/16mm ->1/256mm.
Redness due to the presence of hematite and indicates that the deposition of the silt occured in an oxidizing, probably terrestrial environment. |
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Term
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Definition
Jasper
Dominant Mineral:crystalline quartz.
Easy to identify the quartzm because it is the only common chemical ppt that is hard. |
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Term
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Definition
Travertine
banded or layered calcite resulting from the precipitation of calcite from solution in caves. |
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Term
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Definition
Calcarenite
Lithified, calcareous (made of calcite)sand-sized clasts. Since the rock is 100% calcite it is a limestone.. Grains are produced by weathering, not growth like oolites are so shapes are irregular. |
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Term
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Definition
Graywacke
Clastic
Clay Matrix/Rock Fragments
Lithified clasts having a diameter of 1/16-2.0mm. The name is german meaning "gray stone". Abundant quartz, but always has rock fragments as grains of sand. Presence of clay matrix. To see the clay matrix, poke at the material under the microscope, notice the softness of the material between the grains of sand. |
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Term
Sedimentary
[image]
[image]
[image] |
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Definition
Gypsum
Mono-mineralic rock comprised of gypsum. Test for hardness, gypsum can be scratched with your fingernail. |
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Term
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Definition
Shale
Clastic
Very fine grained, lithified clasts less than 1/256mm in diameter. Grains are invisible and smooth. Fossils help to determine the rock is clastic. |
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Term
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Definition
Flint
Very fine grain dark grey to black crystalline quartz. Easy to identify the quartz because it is the only common ppt that is hard. |
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Term
Metamorphic
[image]
[image]
[image]
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Definition
Muscovite/Biotite Schist
Megascopic
Foliated Crystalline
Texture is due to Muscovite and Biotite |
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Term
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Definition
Slate
Foliated Crystalline
Slaty Cleavage
dull/no sheen |
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Term
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Definition
Granodioritic Gneiss
Foliated Crystalline
Megascopic
Alternating bands of dark and light minerals
Dark Minerals are a combo of horneblende and biotite
Light Minerals are a combo of quartz, orthoclase, and plagioclase
No Pink orthoclase(k-spar) |
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Term
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Definition
Talc Schist
Talc
Greasy/Slippery/Soapy feel
talc only occurs as a metamorphic mineral |
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Term
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Definition
Marble
Random Crystalline
non-foliated
100% Calcite
Dark bands from small amount of graphite
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Term
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Definition
Biotite Schist
Foliated Crystalline
Biotite
Platy Mineral (sheet silicate) |
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Term
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Definition
Garnet Schist
Contains Garnet or Biotite
Foliated Crystalline
Schistose
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Term
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Definition
Phyllite
Microscopic
Foliated
Slaty Cleavage
Has a sheen, is not dull
Sheen is due to growth of tiny mica crystals |
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Term
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Definition
Serpentinite
Foliated Crystalline
Serpentine
Megascopic
Schistose
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Term
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Definition
Quartzite
100% Quartz
Random Crystalline |
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Term
Metamorphic
Chlorite Schist
(no pic) |
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Definition
Foliated, chlorite
Green in color
soft rock less than 2.5
Flexible 1-d flakes
Schistose foliation |
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Term
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Definition
Granitic Gneiss
Foliated Crystalline
Megascopic
Alternating layers of light and dark including some pink
Dark Mineral - Horneblende and biotite
Light Mineral - quartz, pink orthoclase |
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Term
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Definition
Horneblende
Black to green
2-d not at right angles |
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Term
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Definition
Corundum
Barrel-shaped
Hexagonal Habit
Very Hard - 9
Fracture |
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Term
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Definition
Plagioclase
Striations
2-d at 90°
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Term
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Definition
Fluorite
soft
4-D
octahedral |
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Term
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Definition
Olivine
Green and glassy aggregates (microscope)
No cleavage
Fracture
High temp igneous mineral |
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Term
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Definition
Orthoclase (k-spar)
No striations
2-d at 90°
Streak color: white |
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Term
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Definition
Halite
Transparent
Soft 3-D (cubic)
Low temp sedimentary mineral |
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Term
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Definition
Quartz
transparent/translucent
Hard
No Cleavage
Conchoidal Fracture |
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Term
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Definition
Calcite
3-D non 90°
Rhombohedral
HCL Reaction |
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Term
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Definition
Galena
Metallic
Hi SG
3-d Perfect Cubic 90° |
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Term
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Definition
Kaolinite
Looks like chalk
no HCL reaction
1-d (invisible)
Low Temp sedimentary mineral |
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Term
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Definition
Pyrite
Fools Gold
Fracture
Quartz
Metallic, yellowish and hard |
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Term
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Definition
Muscovite
1-d
Perfect Cleavage
colorless/silvery |
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Term
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Definition
Limonite
Yellowish/Orange
Diagnostic: Orange Streak
Earthy |
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Term
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Definition
Calcite
3-D Rhombohedral
HCL Reaction
Low Temp Sedimentary mineral |
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Term
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Definition
Sphalerite
6-D
Diagnostic: Pale yellow streak
resinous |
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Term
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Definition
Serpentine
green, waxy
1-d (usually invisible) |
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