University:
Massachusetts Institute of Technology
Course:
12.109 | Petrology
Academic year:

2024
Views:

52

Pages:

10
Author:

gewoekerdodx

Crystalline Igneous Texture Crystalline Texture Pegmatitic Large crystals > 30mm diameter Early-formed, euhedral crystals surrounded by later-formed subhedral crystals. Crystalline Texture Phaneritic Crystals 30mm – 1mm diameter Early-formed, euhedral crystals surrounded by later-formed subhedral to anhedral crystals Crystalline Texture Phaneritic Finely phaneritic is 1mm – 3mm Medium phaneritic is 3mm – 10mm Coarsely phaneritic is 10mm – 30mm Crystalline Texture Aphanitic Small crystals < 1mm diameter Crystals not generally discernible to eye Crystalline Texture Aphanitic Microcrystalline has microlite crystals that can be identified with a petrographic microscope. Cryptocrystalline has finer-sized crystals that cannot be identified even with petrographic microscope. Crystalline Texture Porphyritic Two distinctly different-sized crystals Large crystals are Phenocrysts Small crystals are Groundmass Crystalline Texture Porphyritic Porphyritic-phaneritic has phenocrysts embedded in phaneritic groundmass. Porphyritic-aphanitic has phenocrysts embedded in aphanitic groundmass. Crystalline Texture Pegmatitic Aphanitic Crystalline Texture Porphyritic-phaneritic Porphyritic-aphanitic

Textures of Igneous Rocks Lecture Part 3

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