Igneous Rock Textures Quiz

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Questions and Answers

What does the term 'phaneritic' refer to?

A fine-grained rock

A coarse-grained rock (correct)

A vesicular rock

A glassy rock

What does the term 'aphanitic' mean?

Contains gas bubbles

Amorphous and formless

Crystals cannot be observed with the naked eye (correct)

Crystals are visible without a microscope

What is the definition of 'porphyritic'?

A rock composed of two or more different sized crystals, with large ones called phenocrysts.

What does 'pegmatitic' describe?

An extremely coarse-grained rock with crystals greater than one centimeter. Signup and view all the answers

What is the meaning of 'vesicular'?

A rock that contains holes formed by gas bubbles. Signup and view all the answers

What does the term 'glassy' mean in rock textures?

A rock that is amorphous and formless. Signup and view all the answers

What does 'pyroclastic' mean?

Composed of broken, angular fragments from a volcanic eruption. Signup and view all the answers

What type of rock is granite?

Felsic in composition, phaneritic in texture. Signup and view all the answers

What is rhyolite's composition and texture?

Felsic in composition, aphanitic in texture. Signup and view all the answers

What type of rock is diorite?

Intermediate in composition, phaneritic in texture. Signup and view all the answers

What is andesite's composition and texture?

Intermediate in composition, aphanitic in texture. Signup and view all the answers

What type of rock is gabbro?

Mafic in composition, phaneritic in texture. Signup and view all the answers

What is basalt's composition and texture?

Mafic in composition, aphanitic in texture. Signup and view all the answers

What is peridotite's composition and texture?

Ultramafic in composition, phaneritic in texture. Signup and view all the answers

What is komatiite's composition and texture?

Ultramafic in composition, aphanitic in texture. Signup and view all the answers

What does 'scoria' describe?

Mafic in composition, vesicular in texture. Signup and view all the answers

What is pumice's composition and texture?

Felsic in composition, vesicular in texture. Signup and view all the answers

What is obsidian's composition and texture?

Mafic in composition, glassy in texture. Signup and view all the answers

What does 'volcanic tuff' mean?

Porphyritic in texture. Signup and view all the answers

Study Notes

Igneous Rock Textures Overview

Phaneritic: Coarse-grained texture with visible crystals, easily observable without a microscope.
Aphanitic: Fine-grained texture where crystals are not visible to the naked eye, indicating rapid cooling.
Porphyritic: Composed of large crystals (phenocrysts) embedded in a finer groundmass, reflecting varied cooling rates.
Pegmatitic: Extremely coarse-grained, crystals often exceeding one centimeter, indicative of slow crystallization in magma.
Vesicular: Contains gas bubbles (vesicles) formed during crystallization, showcasing volcanic activity.
Glassy: Amorphous texture lacking crystals; consists of a random atomic arrangement, formed by rapid cooling.
Pyroclastic: Made of angular fragments from explosive volcanic eruptions, showcasing a mixture of rock sizes.

Specific Rock Types and Their Textures

Granite: Felsic composition with a phaneritic texture, commonly used in construction and countertops.
Rhyolite: Felsic composition and aphanitic texture, often found in volcanic areas, lighter in color.
Diorite: Intermediate composition with a phaneritic texture, known for its speckled appearance of light and dark minerals.
Andesite: Intermediate composition with an aphanitic texture, often associated with volcanic arcs.
Gabbro: Mafic composition characterized by a phaneritic texture, dark in color, commonly found in oceanic crust.
Basalt: Mafic composition, aphanitic texture; prevalent in lava flows, darker and denser than granite.
Peridotite: Ultramafic composition with phaneritic texture, primarily composed of olivine, indicative of the Earth's mantle.
Komatiite: Ultramafic composition and aphanitic texture, ancient volcanic rock reflecting high temperatures during formation.
Scoria: Mafic composition with a vesicular texture, often produced in explosive eruptions, lightweight due to trapped gas.
Pumice: Felsic composition with a vesicular texture, light enough to float on water, formed during explosive volcanic eruptions.
Obsidian: Mafic composition, glassy texture, solid volcanic glass formed from rapid cooling of lava.
Volcanic Tuff: Porphyritic texture, consists of volcanic ash and fragments, often used in construction.

Key Composition Types

Felsic: Light-colored, rich in silica (granite, rhyolite, pumice).
Intermediate: Balanced composition (diorite, andesite).
Mafic: Dark-colored, rich in iron and magnesium (gabbro, basalt, scoria, obsidian).
Ultramafic: Very high in magnesium and iron (peridotite, komatiite).

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Description

Test your knowledge of igneous rock textures with this flashcard quiz. Learn about terms like phaneritic, aphanitic, and porphyritic, and understand their definitions and differences. Perfect for geology students looking to strengthen their vocabulary.