Questions and Answers
What does the term 'phaneritic' refer to?
What does the term 'aphanitic' mean?
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?
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What is the meaning of 'vesicular'?
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What does the term 'glassy' mean in rock textures?
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What does 'pyroclastic' mean?
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What type of rock is granite?
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What is rhyolite's composition and texture?
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What type of rock is diorite?
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What is andesite's composition and texture?
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What type of rock is gabbro?
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What is basalt's composition and texture?
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What is peridotite's composition and texture?
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What is komatiite's composition and texture?
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What does 'scoria' describe?
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What is pumice's composition and texture?
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What is obsidian's composition and texture?
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What does 'volcanic tuff' mean?
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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.
