geo112_lab05_igneous_rx_stations_hand_in
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Stony Brook University *
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112
Subject
Geology
Date
Dec 6, 2023
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docx
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4
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Igneous Rocks
This week we will learn how to recognize, describe, and classify igneous rocks. The following stations
will help you become familiar with properties of igneous rocks.
Station 1
-- Rocks as aggregates of 1 or more mineral(s) (or glass).
How many different minerals do you see? What are they?
Station 2 – Texture
The 2 most common igneous textures are phaneritic and aphanitic.
Define these terms.
Classify the texture of these 2 samples:
A:
B:
Station 3 – Texture part 2
Another texture (commonly associated with volcanic rocks) is porphyritic.
Here are 2 examples, a
porphyritic basalt and a porphyritic andesite.
Look carefully at each sample. Can you see some
commonalities? Based on this, write a definition of porphyritic.
Station 4 – Texture part 3
The last texture is pegmatitic.
Look at this sample and write a definition of pegmatitic.
Station 5 – Composition
The three compositional terms for igneous rocks are felsic, intermediate, and mafic.
Classify the
composition of these 3 samples, based on the color index (fraction of “dark” minerals).
A:
B:
C:
Station 6 –
Rock ID
Describe the texture and composition of this rock, and list the three main minerals present.
What rock is this?
Station 7 –
Rock ID
Describe the texture and composition of this rock.
What rock is this?
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Station 8 – Basalts
Rocks can vary in appearance, even within the same rock type.
These 3 rocks are all basalts. They can be
vesicular (A), non-vesicular (B) or even porphyritic (C).
Yet, they are similar enough that they are still all
basalts. What similarities do you see?
Look at example C.
What is the green mineral (refer to the tables for a hint)?
Station 9 – Granites
Rocks can vary in appearance, even within the same rock type.
These 3 rocks are all granites. Yet, they
are similar enough that they are still all granite. What similarities do you see?
Look at example C.
What is the pink mineral?