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What sequence of events produces porphyritic texture in rocks

User RobM
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For small degrees of undercooling the nucleation rate will be low and the growth rate moderate. A few crystals will form and grow at a moderate rate until they run into each other. Because there are few nuclei, the crystals will be able to grow to relatively large size, and a coarse-grained texture will result. This would be called a phaneritic texture.
User Bgondy
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