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BookmarkVolcanic rock is an igneous rock of volcanic origin.
Volcanic rocks are usually fine-grained or aphanitic to glassy in texture.
They often contain clasts of other rocks and phenocrysts.
Phenocrysts are crystals that are larger than the matrix and are identifiable with the unaided eye.
They were created during fractional crystallization of magma before extrusion.
Rhomb porphyry is an example with large rhomb shaped phenocrysts embedded in a very fine grained matrix..
For more information about the topic Volcanic rock, read the full article at Wikipedia.org, or see the following related articles:
Igneous rock — Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive ... > read more
Pumice — Pumice is a highly vesicular pyroclastic igneous rock of intermediate to siliceous magmas including rhyolite, trachyte and phonolite. Pumice is ... > read more
Basalt rock — Basalt is a common gray to black volcanic rock. It is usually fine-grained due to rapid cooling of lava on the Earth's surface. It may be porphyritic ... > read more
Volcanic cone — Volcanic cones are among the simplest volcano formations. They are built by fragments (called ejecta) thrown up (ejected) from a volcanic vent, ... > read moreNote: This page refers to an article that is licensed under the GNU Free Documentation License. It uses material from the article Volcanic rock at Wikipedia.org. See the Wikipedia copyright page for more details.
