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Physical Geology · Problem type
A rock’s origin from its texture
Use this for “A rock shows aligned mica flakes with a wavy shine. Is it igneous, sedimentary or metamorphic?”
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How did this rock form?
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Texture records how a rock formed: cooling, cementing or recrystallizing.
Assumptions
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Interlocking crystals or glass grew from a melt; grain size tells how fast it cooled.
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Rounded grains, pebbles or shells held by cement were carried, laid down and lithified.
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Aligned flakes, bands or recrystallized grains grew in solid rock under heat and pressure.
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