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BookmarkBasalt 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 containing larger crystals in a fine matrix, or vesicular, or frothy scoria.
Unweathered basalt is black or gray.
Basalt magmas form by decompression melting of peridotite in the Earth's mantle, a process discussed in the entry for igneous rocks.
The crustal portions of oceanic tectonic plates are comprised predominantly of basalt, produced from upwelling peridotite in the mantle below ocean ridges..
For more information about the topic Basalt rock, read the full article at Wikipedia.org, or see the following related articles:
Volcanic rock — Volcanic rock is an igneous rock of volcanic origin. Volcanic rocks are usually fine-grained or aphanitic to glassy in texture. They often contain ... > read more
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
Mid-ocean ridge — A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. This uplifting of the ocean floor occurs when ... > read more
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