Minerals under the microscope

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Minerals under the microscope
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• The MINERALS you need to know
• quartz
• microcline
• plagioclase
• muscovite
• biotite
• amphibole
• pyroxene
• olivine
• garnet
• calcite

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Quartzgrains in sandstone
quartz
quartz
quartz
quartz
XPL
PPL
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Plagioclasewith repeated twinning
plagioclase
plagioclase
XPL
PPL
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Microclinegrain in centre showing its
distinctive cross-hatched twinning
microcline
microcline
XPL
PPL
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Muscovite clear under PPL but with perfect
cleavage and bright interference colours
muscovite
muscovite
XPL
PPL
PPL
XPL
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Biotitepleochroic with one perfect cleavage
strong natural colour masks polarisation colours
making look greenish under XPL
feldspar
feldspar
biotite
biotite
PPL lower view rotated to show pleochroism
XPL
biotite
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Amphibolepleochroic with 2 cleavages at 60o or
120o distinguishing it from biotite or pyroxene
amphibole
amphibole
PPL lower view showing pleochroism
XPL
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Pyroxenewell-formed crystal seen here with 2
cleavages at 90o brightly coloured under XPL
pyroxene
pyroxene enlarged
XPL
PPL
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Olivinelooks like a stained-glass window bright
interference colours and thick black fractures
olivine
olivine
plagioclase
plagioclase
PPL
XPL
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Garnetrounded crystal, transparent under PPL but
goes extinct under XPL
garnet
garnet
XPL
PPL
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Calcitemay show both high and low relief,
transparent under PPL with 2 perfect cleavages
at 120o. Under XPL it shows pearly shades
calcite
calcite
XPL
PPL