Porphyry Identification Quiz

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Questions and Answers

What is the function of crystal size in igneous rocks?

It determines the color of the rock

It is a function of mineral type

It affects the texture of the rock

It is a function of cooling rate (correct)

What is the name for the little crystals in the porphyritic texture?

Microliths

Phenocrysts (correct)

Minites

Nanocrystals

What type of rock would the tuff be classified as?

Sedimentary

Igneous (correct)

Metamorphic

None of the above

What is the name for the process that leads to the formation of porphyritic texture?

Portfolio texture (B) Signup and view all the answers

What is the name for the coarse-grained rock that would have formed if it had continued to cool at a slow rate?

Diorite (A) Signup and view all the answers

What is the first mineral to form when the rock cools down after being heated to 2000 degrees Fahrenheit?

Olivine (A) Signup and view all the answers

What is the last mineral to solidify when the rock cools down?

Quartz (C) Signup and view all the answers

What is Bowen's reaction series?

A mineral crystallization process (A) Signup and view all the answers

What determines where plagioclase feldspar will melt in Bowen's reaction series?

Composition (C) Signup and view all the answers

Which factor determines whether silicate minerals are linked together or exist by themselves?

Metal ions (D) Signup and view all the answers

What does the texture of a rock refer to?

The size, shape, and alignment of minerals in the rock (A) Signup and view all the answers

What type of rock can have a vesicular texture?

Basaltic (A) Signup and view all the answers

What is the difference between glassy and porphyritic textures?

Glassy has no crystals, porphyritic has large crystals surrounded by smaller crystals (C) Signup and view all the answers

What is the definition of a porphyry?

A type of rock with two distinct crystal sizes (A) Signup and view all the answers

What mineral is the most common in igneous rock?

Feldspar (C) Signup and view all the answers

What is the primary difference between the continental and oceanic plates?

The continental plate is primarily made of granite, while the oceanic plate is primarily made of salt. (D) Signup and view all the answers

What is the composition of the mafic rocks?

Almost no quartz or potassium feldspar. (B) Signup and view all the answers

What is the difference between felsic and mafic rocks?

Felsic rocks are lighter in color and higher in feldspar and silica, while mafic rocks are darker in color and higher in iron and magnesium. (A) Signup and view all the answers

What is the meaning of texture in geology?

Texture describes the size, shape, and orientation of the rock itself. (B) Signup and view all the answers

What is the most common type of igneous rock?

Basalt (B) Signup and view all the answers

What is the name of the coarse-grained detrital sedimentary rock?

Conglomerate (A) Signup and view all the answers

What is the primary difference between fine-grained and coarse-grained detrital sedimentary rocks?

Particle size (C) Signup and view all the answers

What is the significance of the angularity of particles in breccia rock?

It indicates a high energy environment (D) Signup and view all the answers

What is Arkose?

A type of sandstone (D) Signup and view all the answers

Which type of rock contains indications of past life or fossils?

Sedimentary rock (A) Signup and view all the answers

What is the most common type of rock found at the surface of the Earth?

Sedimentary rock (C) Signup and view all the answers

What are the two categories of sedimentary rocks?

Chemical and detrital (B) Signup and view all the answers

What is the process that derives sediment for sedimentary rocks?

Weathering and erosion (A) Signup and view all the answers

Where might shale form?

In the middle of the ocean (C) Signup and view all the answers

What is the most common type of rock at the Earth's surface?

Shale (A) Signup and view all the answers

Why do sedimentary rocks typically form in distinct layers?

They were deposited by water (B) Signup and view all the answers

What is the name of the rock that is mainly composed of olivine and a little bit of calcium-rich plagioclase?

Peridotite (D) Signup and view all the answers

What is the order in which minerals crystallize according to Bowen's reaction series?

Olivine, pyroxene, feldspar, quartz (C) Signup and view all the answers

What is exfoliation in the context of weathering?

The cracking and peeling of rock due to changes in pressure (A) Signup and view all the answers

What is the process by which sedimentary rocks are formed?

Deposition and cementation of sediment (C) Signup and view all the answers

What are the three types of sedimentary rocks mentioned in the text?

Chemical, biochemical, and organic (A) Signup and view all the answers

What mineral is commonly found in chemical sedimentary rocks?

Calcite (C) Signup and view all the answers

What is the difference between limestone and travertine?

Limestone is formed from calcium carbonate precipitating directly from water, while travertine is a rock made of pure shells (A) Signup and view all the answers

What are the three agents of metamorphism?

Heat, pressure, and chemically active fluids (B) Signup and view all the answers

What is the difference between clastic and chemical sedimentary rocks?

Clastic rocks are formed from sediments that have been transported and deposited, while chemical rocks are formed from minerals that precipitate out of solution (A) Signup and view all the answers

What is foliation in metamorphic rocks?

The layering or alignment of mineral grains in metamorphic rocks (D) Signup and view all the answers

Where are fossils primarily found?

In sedimentary rocks (D) Signup and view all the answers

Study Notes

Sedimentary and Metamorphic Rocks

Sedimentary rocks are formed from the accumulation of sediments and are classified based on the size and composition of the grains.
Sedimentary rocks can also be classified based on their origin, such as clastic, chemical, and organic.
Clastic sedimentary rocks are made up of fragments of pre-existing rocks, while chemical sedimentary rocks are formed from minerals that precipitate out of solution.
Organic sedimentary rocks are made up of the remains of once-living organisms.
Sedimentary rocks are typically laid down in layers, which record past environments and can contain fossils.
Metamorphic rocks are formed from pre-existing rocks that have undergone changes in temperature, pressure, and mineral composition.
Metamorphic rocks can be foliated or non-foliated, with foliation referring to the alignment of mineral grains.
Examples of foliated metamorphic rocks include slate, phyllite, schist, and gneiss.
Non-foliated metamorphic rocks include marble and quartzite.
The agents of metamorphism are heat, pressure, and chemically active fluids.
Mineral resources can be found in both sedimentary and metamorphic rocks, such as gold in the California Gold Rush.
Fossils are primarily found in sedimentary rocks, with invertebrates being the most common due to their hard parts.

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Description

Identifying Porphyry: Test your knowledge on the characteristics of porphyry rocks, including the presence of phenocrysts and ground mass. Learn how to differentiate between porphyry and other rock types through this quiz.