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Native elements |
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sulfur |
S |
1)
fumaroles, 2) within sediments as a result of bacterial reduction of sulfate
minerals |
celestite,
gypsum, anhydrite, carbonate minerals |
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Nesosilicates |
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topaz |
Al2SiO4(F,OH)2 |
1) late stage igneous crystallization or adjacent
hydrothermal veins, 2) contact aureoles adjacent to silicic plutons |
quartz, feldspar, muscovite, tourmaline, fluorite,
cassiterite, apatite, beryl |
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Tectosilicates |
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sanidine |
KAlSi3O8 |
1) in silicic igneous rocks that have cooled
quickly; tuffs and rhyolite flows are most common |
quartz and micas |
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Quartz is present in many felsic igneous lava
flows and tuffs, sometimes forming euhedral crystals. In very hot flows and
tuffs, the polymorphs cristobalite and tridymite may occur, along with other
volcanic primary and pneumatolitic minerals. |
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Native elements |
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diamond |
C |
1)
altered ultramafic rocks of mantle origin, 2) placer deposits |
pyrope,
olivine, kyanite, zircon, pyroxenes |
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Oxides |
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chromite |
FeCr2O4 |
1)
ultramafic rocks, 2) placers & black sands |
olivine,
pyroxene, spinel, magnetite, sulfides |
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Nesosilicates |
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FORSTERITE |
Mg2SiO4 |
1) mafic and ultramafic igneous rocks,
2) metamorphosed serpentinites, 3) metamorphosed carbonates |
pyroxenes, plagioclase, spinel, garnet, serpentine |
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Fayalite is the Fe end member of the olivine group
(Fe2SiO4); it is found in Fe-rich granitic rocks and Fe-rich metamorphic
rocks. |
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Phyllosilicates |
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phlogopite |
KMg3AlSi3O10
(OH)2 |
1) marble, 2) ultrabasic igneous rocks |
calcite, dolomite, quartz, diopside, and tremolite |
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Tectosilicates—feldspathoid
group |
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leucite |
K
feldspathoid |
1) silica poor, K-rich volcanic rocks |
quartz is an anti-association |
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nepheline |
Na
feldspathoid |
1) silica poor igneous rocks |
feldspars, apatite, cancrinite, sodalite, zircon,
biotite |
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sodalite |
Na
feldspathoid with Cl |
1) silica poor, alkali rich igneous rocks |
nepheline, cancrinite, leucite, feldspars |