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Igneous Rock Textures
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Ophitic
Ophitic texture is found in dolerites where pyroxene surrounds and encloses plagioclase feldspar, signifying a slower rate of cooling that allows pyroxene crystals to envelop the earlier-formed feldspar.
Phaneritic
Phaneritic texture features coarse grains, indicating that the rock crystallized slowly from magma deep underground.
Equigranular
Equigranular texture has minerals that are roughly the same size, suggesting a uniform rate of cooling and crystallization.
Frothy
Frothy texture is characterized by a high volume of vesicles, like in pumice, indicating extremely rapid cooling with high gas content and facilitates floating on water.
Aphanitic
Aphanitic texture is characterized by fine grains that cooled quickly on or near the Earth's surface, often too small to see with the naked eye.
Glassy
Glassy texture forms when magma cools so rapidly that atoms cannot arrange into a crystal structure, resulting in a non-crystalline material like obsidian.
Pyroclastic
Pyroclastic texture consists of fragmented material due to explosive volcanic eruptions; these fragments can be volcanic ash, pumice, or lava bombs.
Pegmatitic
Pegmatitic texture contains extremely large crystals, forming in environments with abundant water that allows elements to travel and crystallize easily.
Porphyritic
Porphyritic texture displays large crystals (phenocrysts) embedded in a matrix of smaller crystals (groundmass), indicating a complex cooling history.
Vesicular
Vesicular texture is marked by many cavities or bubbles (vesicles) caused by gas trapped in the lava during the rapid cooling of an extrusive eruption.
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