Igneous Rock Textures

Terms	Definitions
aphanitic texture	a texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished with the unaided eye (fine-grained)
vesicular texture	a term applied to aphanitic igneous rocks that contain many small cavities, called vesicles (fine-grained)
phaneritic texture	an igneous rock texture in which the crystals are roughly equal in size and large enough so that individual minerals can be identified with the unaided eye (coarse-grained)
porphyritic texture	an igneous rock texture characterized by two distinctively different crystal sizes. The larger crystals are called phenocrysts, and the matrix of smaller crystals is termed the groundmass.
glassy texture	a term used to describe the texture of certain igneous rocks, such as obsidian, that contain no crystals
pyroclastic texture	an igneous rock texture resulting from the consolidation of individual rock fragments that are ejected during a violent eruption
pegmatitic texture	a texture of igneous rocks in which the interlocking crystals are all larger than one centimeter in diameter

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7 terms