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Fine-Grained (Aphanitic) Textures - University of Pittsburgh

Fine-grained textures generally indicate magmas that rapidly cooled at or near the Earth's surface. Fast cooling prevents crystals from growing very large. The cutoff between fine- and coarse-grained textures is about 1 mm. All four photos below are of the mafic rock basalt. The more felsic ...

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Igneous rocks - University of Auckland

Igneous rocks. Igneous rocks are formed by the solidification of magma, a silicate liquid generated by partial melting of the upper mantle or the lower crust. Different environments of formation, and the cooling rates associated with these, create very different textures and define the two major groupings within igneous rocks:

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Aphanitic | Encyclopedia

Aphanitic, extrusive, igneous rocks therefore have coarse-grained, intrusive counterparts with the same chemical and mineral composition. For example, the silica-rich extrusive rock, rhyolite, common in continental volcanic regions, is the fine-grained equivalent of intrusive granite.

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Igneous Rock Texture - hyperphysics.phy-astr.gsu.edu

Aphanitic Rock Aphanitic rock is igneous rock in which the grain or crystalline structure is too fine to be seen by the unaided eye. Such rock is formed when the material solidifies at or near the surface so that the cooling is rather rapid. Such rocks are termed "extrusive" rocks.Under these conditions, there is not enough time for the growth of large crystals.

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Igneous Rocks | Geology

Igneous textures include the rock textures occurring in igneous rocks. Igneous textures are used by geologists in determining the mode of origin igneous rocks and are used in rock classification. There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic.

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What is a porphyritic igneous rock? - Quora

Sep 18, 2016 · Thanks for the A2A. Igneous rock is formed through the cooling and solidification of magma or lava and is one of the three main rock groups, the two others being sedimentary and metamorphic. The word igneous comes from the Latin term ignis, which ...

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What Is the Difference Between Phaneritic and Aphanitic Rocks?

Crystalline rocks with mineral grains that cannot be distinguished from one another without magnification have an aphanitic igneous texture. Igneous rocks form by crystallization of minerals from liquid magma rising into the upper portion of Earth's crust from the lower crust and underlying mantle.

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Introduction to Igneous Rocks - csmgeo.csm.jmu.edu

An introduction to igneous rocks requires exploration of three core ideas. Each of these is introduced simplistically below, and then further explored in other pages of the site. Formation, Classification, and Identification of Igneous Rocks (next). Igneous rock evolution Plate tectonics and igneous rock .

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Igneous Rocks- Chapter 4 Flashcards | Quizlet

the rock is crystalline; mineral grains are too small to be visible without a magnifying lens or microscope An _ texture would be most unlikely to occur in an extrusive igneous rock aphanitic

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Igneous Rock Identification - Chemeketa Community College

Texture - Aphanitic (fine grained) Step 2. The identification of aphanitic-textured igneous rocks can often be frustrating. When no minerals are visible we have to rely on color, a poor means of identifying a rock. When a few mineral grains are present as phenocrysts in a fine-grained matrix, these can be very helpful in the identification.

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Igneous Rocks - soest.hawaii.edu

11 Photomicrograph of Granite Classification of Igneous Rocks Based on Mineral Composition and Texture Textures-reflect rate of cooling• Phaneritic-mineral crystals are visible e.g. Granite & Gabbro• Pegmatite-exceptionally large crystals e.g. Pegmatite• Aphanitic-crystals not visible e.g. Rhyolites & Basalt• Porphyritic-large crystals surrounded by small crystals-

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The Texture of Igneous Rocks - Geology In

Igneous textures include the rock textures occurring in igneous rocks. Igneous textures are used by geologists in determining the mode of origin igneous rocks and are used in rock classification. There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic.

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Physical Geology Lab Samples

PART I - Volcanic (Extrusive) Rocks. BASALT. Basalt is an extrusive mafic volcanic rock. It is commonly erupted as passive lava flows due to its low viscosity (resulting from high magmatic temperatures and low silica contents). A dominant component of oceanic crust, basalt is the most abundant volcanic rock. Texture: aphanitic

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Igneous Rocks 101 | NC DNCR Office of State Archaeology

For example a smooth igneous rock was cooled very fast because it is has small crystals and is therefore an extrusive rock. The texture of this rock would be called fine grained or aphanitic. In the reverse situation an igneous rock that cooled very slowly and formed large grains would be described as having a coarse grained or phaneritic texture.

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Is diorite's texture a aphanitic - answers

The three main categories of igneous rock texture are aphanitic, phaneritic, and porphyritic. Aphanitic texture is described as a crystalline igneous structure that is too small to be seen with ...

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Igneous rock - Wikipedia

Igneous rock (derived from the Latin word ignis meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust.

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Igneous Rock Textures - Indiana University Bloomington

Igneous Rock Textures. COARSE GRAINED TEXTURE (), mineral grains easily visible (grains several mm in size or larger)A hand specimen of granite with phaneritic (coarse grained) texture. Principal minerals are Potassium Feldspar, Biotite Mica, and Quartz.

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Igneous Rocks - soest.hawaii.edu

11 Photomicrograph of Granite Classification of Igneous Rocks Based on Mineral Composition and Texture Textures-reflect rate of cooling• Phaneritic-mineral crystals are visible e.g. Granite & Gabbro• Pegmatite-exceptionally large crystals e.g. Pegmatite• Aphanitic-crystals not visible e.g. Rhyolites & Basalt• Porphyritic-large crystals surrounded by small crystals-

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Igneous Rocks: Formation Texture and Composition | Geology

The table below shows classification of major groups of igneous rocks based on their mineral composition and texture: Note: An igneous rock rich in SiO 2 is termed acidic. The SiO 2 may occur as free quartz or be combined with varying proportions of elements to form minerals such as feldspar.

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Igneous rock - ipfs.io

Igneous rock (derived from the Latin word ignis meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust.

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