4) Sedimentary, near-surface, & weathering minerals G 232
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Oxides |
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hematite (hehm'-uh-tight) |
Fe2O3 |
1)
as a cement in sandstones, 2) sedimentary iron formations (usually
metamorphosed), 3) accessory mineral in igneous rocks, 4) hydrothermal veins,
5) altered/oxidized zones in ore deposits |
quartz,
magnetite, Fe bearing sulfides, Fe-rich silicates, Mn-rich
minerals |
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Special
comments: most important ore of iron.
Extremely common. |
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pyrolusite |
MnO2 |
1)
secondary mineral formed in cracks, coatings on surfaces, as nodules, and in
beds |
barite,
limonite, romanechite, hematite, magnetite, other
Fe & Mn oxides |
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Hydroxides |
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manganite |
MnO(OH) |
1)
secondary veins |
Mn oxides and hydroxides, carbonate minerals,
limonite, barite |
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goethite (gay'-thight, etc.) |
FeO(OH) |
extremely
common secondary mineral found in 1) sediments, 2) gossans, 3) laterites |
siderite,
pyrite, magnetite, and many others |
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(bauxite) |
mixture:
diaspore, gibbsite, and boehmite—all
are Al hydroxides |
1)
secondary, as a product of intense weathering leading to aluminous soils |
bauxite
normally contains gibbsite, diaspore, and boehmite; limonite |
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|
(limonite) |
mixture:
hydrous iron oxides |
1)
forms under oxidizing conditions near the surface from iron rich minerals |
siderite,
pyrite, magnetite, and many others |
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|
Term
for natural hydrous iron oxides. May
be amorphous, commonly mostly goethite. |
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romanechite |
Ba-Mn hydroxide, usually mixed
with other Mn oxides and hydroxides. |
1)
secondary mineral in near-surface deposits |
pyrolusite, manganite,
calcite, hematite |
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A
hard, botryoidal mixture was formerly called psilomelane. A
soft mixture has been called wad. |
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Sulfates |
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barite |
BaSO4 |
1)
gangue mineral in hydrothermal veins, 2) veins in limestone, 3) residual in
clays |
fluorite,
galena, quartz, calcite, dolomite, clay minerals |
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Carbonates |
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calcite
|
CaCO3 |
1)
limestone and marble, 2) cave deposits, 3) vein mineral with other
carbonates, sulfates, and sulfides, 4) cement in clastic
sedimentary rocks, 5) in rare igneous rocks (carbonatites),
6) weathering product, 7) shells & skeletal material, 8) wide variety of
metamorphic rocks at low to medium grade |
quartz,
aragonite, dolomite, sulfide and sulfate minerals, clay minerals, many
metamorphic minerals (phyllosilicates, feldspar,
oxides) at low to medium grade |
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aragonite
|
CaCO3 |
1)
disseminated in gypsum beds, 2) hot spring deposits, 3) in sedimentary Fe ore
deposits, 4) oxidized zones within ore deposits, 5) cave formations, 6) blueschist facies metamorphic
rocks, 7) shells and other organic carbonate material |
gypsum,
siderite, celestite, sulfur, limonite, calcite,
malachite, azurite, smithsonite, cerussite |
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dolomite
|
CaMg(CO3)2 |
1)
carbonate sedimentary rocks, 2) hydrothermal veins, 3) alteration after
calcite |
calcite
and other carbonates, fluorite, barite, quartz |
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siderite |
FeCO3 |
1)
sulfide veins, 2) primary in various sedimentary rocks, 3) replacement
mineral in limestone, 4) low T metamorphic rocks |
galena,
pyrite, chalcopyrite, tetrahedrite, clay minerals,
calcite, low T metamorphic minerals |
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