| 21. | The predominant igneous rock is porphyritic hornblende diorite.
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| 22. | Porphyritic dacites contain blocky highly zoned plagioclase phenocrysts and / or rounded corroded quartz phenocrysts.
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| 23. | Porphyritic rocks are formed when a column of rising magma is cooled in two stages.
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| 24. | Some are equigranular, others are porphyritic.
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| 25. | The dacites have a white porphyritic appearance.
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| 26. | The appearance of Lastarria lavas is porphyritic.
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| 27. | It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite.
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| 28. | However, porphyritic varieties do occur.
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| 29. | The lavas of Taftan are porphyritic.
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| 30. | This lava dome is formed by porphyritic andesite and has dimensions of at an altitude of.
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