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| ES0610 |
Coarse-Grained Igneous Rocks |
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! Read
the questions below each image.
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| Matthew Nyman, TERC |
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Is the rock generally
light colored with dark crystals spread
throughout? If yes, your sample is probably
granite. Granite usually takes on the color
of the feldspar crystals in it.
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| Matthew Nyman, TERC |
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Is your rock dark
colored? If yes, your sample is probably
gabbro. Due to the dark color of gabbro,
individual minerals may be hard to see.
Look for crystal surfaces that reflect light.
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| Matthew Nyman, TERC |
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Does your rock have roughly the same
number of light and dark crystals, or appear a gray color overall?
If yes, your sample is probably diorite.
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If you have identified your sample, return to the beginning
of the rock identification
key, select another rock sample, and begin the process
over again.
If your rock sample does not have any of the features
described on this page, reexamine the rock with a hand
lens or magnifying glass. Look at the sample from all
angles. Concentrate on fresh surfaces where you might
be able to better determine the texture. Return to the
beginning of the rock identification
key and start over again.
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