2) Rocks of granitic composition & granitic pegmatites G 232
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Cyclosilicates |
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beryl |
Be3Al2Si6O18 |
1) granitic pegmatites, 2) schists |
K-feldspar, albite, muscovite, quartz |
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(TOURMALINE) |
Na, Ca, Li, Mg, Al, Fe, Mn, B hydrous
cyclosilicate |
1) granitic igneous rocks and pegmatites,
2) metamorphic rocks |
quartz, K-feldspar, lepidolite, beryl, apatite,
spodumene, fluorite, quartz, albite, muscovite |
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'Tourmaline'
is the name of a group of seven minerals; elbaite [pink], schorl [black], and
dravite [brown] are among the most common |
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Phyllosilicates
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muscovite |
KAl3Si3O10(OH)2 |
1) silicic to intermediate igneous rocks, 2) detrital
in e.g. arkose, 3) metamorphic rocks, low-high T |
other micas, K-feldspar, quartz |
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biotite |
K(Fe,Mg)3AlSi3O10(OH)2 |
1) igneous rocks, 2) metamorphic rocks,
3) immature sediments |
other micas, amphiboles, quartz, feldspar |
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biotite is the mineral having intermediate
compositions between the Mg end member phlogopite, and the Fe2+
end member annite |
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lepidolite |
Li,
F, Al mica |
1) Li-rich pegmatites |
tourmaline, amblygonite, spodumene, muscovite,
feldspar, quartz |
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Tectosilicates |
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microcline & orthoclase |
KAlSi3O8 |
1) silicic igneous rocks, 2) arkose,
3) metamorphic rocks; can form from cooling of orthoclase and sanidine |
quartz and micas |
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Can only be distinguished microscopically by the
presence of tartan twinning. However, green K-feldspar is almost certainly
microcline, specifically the variety called amazonite (the |
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3) Minerals of intermediate to mafic igneous rocks
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Inosilicates |
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enstatite |
MgSiO3 |
1) mafic igneous rocks, 2) high-T metamorphic
rocks |
plagioclase, clinopyroxene, olivine, garnet |
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Hypersthene is a varietal name given to
intermediate Mg-rich compositions, while bronzite (in allusion to a
bronze-like color) is the name given to Mg-rich compositions. Ferrosilite is the Fe end member of
the solid solution. |
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diopside- |
CaMgSi2O6-CaFeSi2O6 |
1) mafic and ultramafic igneous rocks, 2) marble,
3) medium to high grade metamorphic rocks |
plagioclase, hornblende, olivine; calcite, quartz,
forsterite, tremolite, scapolite, garnet; garnet, epidote |
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Hedenbergite
(head'-n-berg-ight) is the Fe end member of the clinopyroxenes. |
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augite |
Ca,Na,Mg,Fe,Al
clinopyroxene |
1) mafic to intermediate volcanic and plutonic
igneous rocks |
hornblende, plagioclase |
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(hornblende) |
Ca,
Na, Mg, Fe, Al clinoamphibole |
1) common in a wide variety of igneous rocks, 2)
metamorphosed intermediate to mafic igneous rocks |
plagioclase, quartz, K-feldspar; garnet, epidote,
magnetite, ilmenite, rutile |
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There are two minerals that comprise hornblende
sensu stricto; these are magnesiohornblende and ferrohornblende. There are
several other amphibole species that are commonly referred to as
'hornblende'. |
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