Earth Science Rock Identification (Ref Table P6-7)

State the name of the igneous rock in which crystals of biotite mica are larger than 10 millimeters in diameter

The diagram represents a portion of the scheme for igneous rock identification. Line AB represents the percentages of the minerals in igneous rock 1 and line CD represents the percentages of the minerals in igneous rock 2. Rock 1 is a glassy, vesicular igneous rock. Identify the name of rock 1

The diagram represents a portion of the scheme for igneous rock identification. Line AB represents the percentages of the minerals in igneous rock 1 and line CD represents the percentages of the minerals in igneous rock 2. Compared to the color and density of igneous rock 1, describe how the relative color and density of igneous rock 2 are different.

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Answer explanation

Relative color of rock 2:

— Igneous rock 2 is darker/dark. — blacker/black
— greener/green
— Rock 1 is lighter than rock 2.

Relative density of rock 2:

• —  Igneous rock 2 has a higher density.

• —  greater

• —  more dense/denser

• —  Rock 1 is less dense than rock 2.

Note: Do not accept “more mafic” for either relative color or relative density of rock 2, as this refers to composition.

Explain why andesite and diorite can both have the same percentage of mineral composition by volume, and yet be two different igneous rocks.

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Which igneous rock could physically weather to beach sand that contains the minerals pyroxene, plagioclase feldspar, and olivine?

• gabbro

• granite

• dunite

• peridotite

What is the texture of an igneous rock formed from magma that cooled slowly deep underground?

• nonvesicular and coarse

• nonvesicular and glassy

• vesicular and fine

• vesicular and very coarse

Which igneous rock formed from magma that cooled slowly and is composed of 5% amphibole, 8% biotite, 15% plagioclase feldspar, 37% quartz, and 35% potassium feldspar?

• rhyolite

• granite

• diorite

• scoria

Identify the general characteristics of color and density of an igneous rock composed of only the minerals olivine and pyroxene.

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Which two minerals would most likely be found in the igneous rock if the rock is highly mafic?

• quartz and potassium feldspar

• olivine and potassium feldspar

• quartz and pyroxene

• olivine and pyroxene

The limestone is composed mostly of what mineral?