identifying common igneous rocks igneous rocks are composed of a variety of minerals that contribute...
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Identifying Common Igneous Rocks
Igneous rocks are composed of a variety of minerals that contribute important classification characteristics.
Click here to see two classification methods
FineCoarse
Intermediate
ColorLight Color Dark Color
Step 1: Describe the rock’s texture
Step 2: Describe the rock’s color.
Step 3: Where does this place you on the chart and what is the name of this igneous rock?
Click on a name in the chart to find out if you are correct.
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FineCoarse
Intermediate
ColorLight Color Dark Color
Step 1: Describe the rock’s texture
Step 2: Describe the rock’s color.
Step 3: Where does this place you on the chart and what is the name of this igneous rock?
Click on the name to find out if you are correct.
NextBack
FineCoarse
Intermediate
ColorLight Color Dark Color
Step 1: Describe the rock’s texture
Step 2: Describe the rock’s color.
Step 3: Where does this place you on the chart and what is the name of this igneous rock?
Click on the name to find out if you are correct.
NextBack
FineCoarse
Intermediate
ColorLight Color Dark Color
Step 1: Describe the rock’s texture
Step 2: Describe the rock’s color.
Step 3: Where does this place you on the chart and what is the name of this igneous rock?
Click on the name to find out if you are correct.
NextBack
FineCoarse
Intermediate
ColorLight Color Dark Color
Step 1: Describe the rock’s texture
Step 2: Describe the rock’s color.
Step 3: Where does this place you on the chart and what is the name of this igneous rock?
Click on the name to find out if you are correct
NextBack
Small CrystalsLarge Crystals
Intermediate
ColorLight Color Dark Color
Step 1: Describe the rock’s texture
Step 2: Describe the rock’s color.
Step 4: Where does this place you on the chart and what is the name of this igneous rock?
Click on the name to find out if you are correct
NextBack
Step 3: This rock is known for its salt and pepper appearance.
Vesicular
Vesicular
Glassy
OrThis is light colored PUMICE. Which term best describes its texture?
These three igneous rocks are not on the texture vs. color chart. Can you pick out the characteristic that helps identify each one?
This is dark colored SCORIA. Which term best describes its texture?
Vesicular Glassy
Pumice and scoria are both full of empty gas voids. In pumice, the tiny voids are not well interconnected. The larger ones in scoria are interconnected. Is this enough of a hint to figure out pumice’s unique characteristic?
Vesicular? Click here
See answer!
This is black OBSIDIAN. Which term best describes its texture?
Glassy
Or
Or
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Pumicefloats on
water!
Igneous Rock Texture, Cooling Rate, and Origin Location
In most cases, the texture of an igneous rock provides a clue that suggests how quickly, in relative terms of fast vs. slow, the molten magma or lava took to cool into solid rock. The concept is really simple:
The slower the molten material cooled, the coarser the texture of the igneous rock.
An extension of this idea is that molten magma or lava will cool differently depending on physical location.
Lava, molten rock expelled onto Earth’s surface, will cool relatively quickly.
On the other hand, magma, molten rock trapped inside Earth, will cool much more slowly.
Can you develop a simple conceptual model that explains this phenomena?
Think you understand? Complete the following sentence by clicking on the correct response.
inside Earth.
on Earth’s surface.
lava
magma
You should be able to construct a similar sentence for the coarse grained igneous rocks, such as granite.
Basalt, a fine grained igneous rock formed as a molten mass of
cooled
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Click here to check your idea
Now for the really good stuff!!
The mineral composition and chemistry of rhyolite and granite are the same! The only difference is their texture due to cooling rate. Which is the intrusive version? Click a photograph below to confirm your answer
The mineral composition and chemistry of gabbro and basalt are the same. The only difference is their cooling rate. Which is the extrusive version? Click a photograph below to confirm your answer.
Obsidian is a well known volcanic rock. Its texture is fine grained and looks like glass. It also breaks with the same kind of unique conchoidal fracture pattern that glass does. Is obsidian intrusive or extrusive? What event(s) had to transpire to turn molten rock into a hunk of black glass? And, what’s conchoidal? Time for you to do some research on your own.
Granite
Obsidian
RhyoliteGabbro Basalt
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Almost done!
Apply your knowledge of igneous rocks.
1. Print the next page.
2. Name the five igneous rocks. Write the name of the rock beside it on your printed page.
3. Ask your teacher to verify your decision.
4. Be prepared to explain the process you used to identify each rock.
5. The pictures are new. Don’t memorize images of rocks, use the process of characteristics.
6. The last page is an expanded version of the igneous rock chart. It may be of help.
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This is ___________________
This is ___________________
This is ___________________
This is ___________________
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