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24 Cards in this Set
- Front
- Back
18 GRANITE
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phaneritic, felsic igneous rock; sometimes porphyritic with large
orthoclase crystals; intrusive origin; look for quartz and orthoclase (but note that orthoclase is not always pink). |
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SANDSTONE-
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-clastic sedimentary rock composed of sand-sized quartz grains; most
quartz sandstones contain highly rounded grains; will scratch glass if strongly cemented. |
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SCHIST
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-Foliated, phaneritic metamorphic rock containing primarily one type of
mineral (muscovite, biotite, or amphibole); sometimes dominated by muscovite mica with ‘chocolate chips’ of garnet. |
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CONGLOMERATE
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Clastic sedimentary rock composed of rounded pebbles and
gravel (a pebble is anything larger than 2 mm); look for the rounded pebbles and check the size |
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GABBRO
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phaneritic, mafic igneous rock; usually dark, and usually dominated by
plagioclase feldspar crystals; look for large, reflecting cleavage surfaces (of plagioclase); you may even see the distinctive striations characteristic of plagioclase, and, more rarely, the blue iridescence of some types of plagioclase. |
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DIORITE
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Phaneritic, igneous rock of intermediate composition; look for the absence
of quartz; usually has a ‘salt and pepper’ appearance with black and white being nearly 50-50. |
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RHYOLITE-
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Aphanitic, felsic, igneous rock; usually pink, purple, or white; often
contains phenocrysts of quartz and/or feldspar; look for the color and quartz phenocrysts (you probably will need the microscope). |
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DOLOSTONE
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Chemical sedimentary rock, like limestone, but composed of the
mineral dolomite; will fizz only when powdered; gray, tan, buff, or even pinkish; it is a building stone used extensively on campus (Old Main, the entrance arch to Johnson Union). |
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GNEISS
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--Foliated metamorphic rock consisting of alternating folia or stringers of
different minerals (usually quartz, feldspar, amphibole, and mica); look for the layering (foliation) and alternating bands of color. |
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ANDESITE
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Aphanitic, typically porphyritic igneous rock of intermediate composition,
as opposed to rhyolite and basalt. Andesite is usually gray; our tray samples have phenocrysts of hornblende, but many andesites do not. Plagioclase is also a common phenocryst mineral. |
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MARBLE
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-Nonfoliated metamorphic rock made of calcite; will not scratch glass;
equigranular; fizzes with HCl; may be a variety of colors. metamorphosed limestone. |
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SHALE
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-Aphanitic, layered clastic sedimentary rock; made of silt and clay grains too
fine to see with the eye; softer than slate, has a dull sound when tapped. |
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BASALT
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Aphanitic, mafic, igneous rock; rarely has phenocrysts, occasionally has
vesicles (air bubbles); black; 75% of the Earth’s surface (mostly the ocean floor) is composed of this rock. |
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PUMICE
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Highly vesicular, felsic glass (obsidian); often light enough to float on
water. Forms as a “froth” on vesiculating felsic magmas, usually associated with violent eruptions. |
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SCORIA
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Vesicular, mafic, igneous rock; look for the bubbly or spongy texture;
formed by the extrusion of gaseous basaltic (mafic) magma; often reddish due to iron oxides. |
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SLATE
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-Foliated, aphanitic metamorphic rock produced by metamorphism of shale;
usually black but may be red or green; harder than shale; often has more of a ringing sound when tapped (compare to the shale). |
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OBSIDIAN
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Aphanitic, felsic, glassy igneous rock; usually black, but sometimes
rusty red; look for conchoidal fracture; this rock cooled so quickly that crystals were unable to form. |
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QUARTZITE
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Nonfoliated metamorphic rock composed entirely of quartz; formed
from the metamorphism of quartz sandstone; extremely hard; has distinct appearance caused by fracture through quartz grains; will easily scratch glass; many of our samples are pink, but quartzite can also be white, gray, tan, or purple. |
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PERIDOTITE
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-Phaneritic (intrusive) igneous rock composed almost entirely of
olivine; ultramafic; green. |
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ROCK GYPSUM
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-Layered or non-layered chemical sedimentary rock composed
entirely of gypsum; will not fizz; will scratch with your fingernail; an evaporite. |
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BRECCIA-
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-Clastic rock composed of angular, pebble-sized fragments. Usually
sedimentary in origin, but can also be igneous. May also be associated with fault zones as a product of deformation. |
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CHERT
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-Aphanitic sedimentary rock composed of quartz; will not fizz; smooth
fracture surface; is harder than glass; may have fossil molds in it; gray, white, red, black, or striped. |
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LIMESTONE
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Chemical or biochemical sedimentary rock composed of calcite, often
with fossils; fizzes readily with HCl. Much limestone is formed by breakdown of organically produced calcium carbonate (such as shells, corals, etc), with subsequent chemical modification. |
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COAL
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Black, light (low density), dull to "glassy", but not as shiny or hard as
obsidian; leaves black streak |