1) Quartz, plagioclase, and common accessory minerals G 232
Quartz (tectosilicate)
|
a (low) quartz |
SiO2 |
1) common and essential mineral in many igneous,
sedimentary, and metamorphic rocks, 2) dominant mineral in many beach
sands, soils, and other sediments |
vast array of associations depending upon the
environment; more important are anti-associations--forsterite, corundum,
feldspathoids, spinel, etc. |
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Coarsely
crystalline varieties of quartz
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rock
crystal (colorless) |
amethyst
(purple) |
rose
quartz (pink) |
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smoky
quartz (brown) |
citrine
(yellow) |
milky
quartz (white) |
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Microcrystalline
fibrous varieties of quartz (chalcedony) |
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agate
(alternating layers of various colors of chalcedony; layers may be curving or
concentric) |
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onyx
(layered in parallel planes) |
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Microcrystalline
granular varieties of quartz |
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flint
(dark) |
chert
(light) |
prase
(green) |
jasper
(red) |
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Plagioclase (tectosilicate)
|
ALBITE |
NaAlSi3O8 |
1) pegmatites, 2) silicic igneous rocks,
3) low temperature metamorphic rocks |
quartz, micas, alkali feldspars |
|
oligoclase, andesine, labradorite,
bytownite |
An10-30,
An30-50, An50-70, An70-90,
|
1)
metamorphic rocks (especially more sodic; 2) igneous volcanic and
plutonic rocks (especially more calcic ones) |
quartz,
amphiboles, micas, pyroxenes |
|
anorthite |
CaAl2Si2O8 |
1) high-temperature mafic igneous rocks, 2) rare
in metamorphosed carbonates |
amphibole, pyroxene, olivine, carbonate and
calc-silicate minerals |
Common Accessory Minerals
|
Sulfides |
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pyrrhotite (peer'-uh-tight) |
Fe1-xS
x=0.0-0.2 |
1)
mafic igneous rocks, 2) pegmatites, 3) contact aureoles, 4) vein deposits |
pyrite,
pentlandite, galena, magnetite, chalcopyrite |
|
PYRITE |
FeS2 |
1)
accessory mineral in many igneous, sedimentary, metamorphic rocks, 2) sulfide
deposits, 3) diagenetic, replacing coal, wood, shells |
many
sulfide minerals: pyrrhotite, arsenopyrite, galena, sphalerite, chalcopyrite,
etc. |
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Oxides |
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ilmenite |
FeTiO3 |
1)
hydrothermal veins, 2) masses in plutonic igneous rocks and pegmatites, 3) in
black sands (placers) |
quartz,
hematite, magnetite, rutile, zircon, monazite |
|
magnetite |
Fe3O4 |
Accessory
mineral in many types of 1) igneous rocks, 2) metamorphic rocks,
3) sedimentary rocks, 4) sediments |
a
vast number: quartz, feldspar, amphibole, pyroxene, and other Fe and Ti
oxides |
|
rutile |
TiO2 |
1)
intermediate to mafic igneous rocks, 2) metamorphic rocks, 3) in veins, 4) in
pegmatites, 5) detrital in sediments and sedimentary rocks |
quartz,
feldspar, ilmenite, hematite |
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Phosphates |
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(apatite)
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F-, |
1)
common accessory mineral in igneous rocks, 2) common accessory mineral in
metamorphic rocks, 3) hydrothermal veins, 4) marine sediments |
very
large number of igneous, metamorphic, and hydrothermal vein minerals |
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Note: the three apatites are chlorapatite,
fluorapatite, and hydroxylapatite |
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Nesosilicates |
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ZIRCON |
ZrSiO4 |
1) igneous rocks, especially silicic ones,
2) common accessory in metamorphic rocks, 3) detrital |
feldspars, quartz, micas, amphiboles, pyroxenes |
|
TITANITE |
CaTiSiO5 |
1) silicic to intermediate igneous rocks, 2)
common in metamorphic rocks |
pyroxene, amphibole, feldspar, quartz |